An Automatic Transmission Question for PhyrraM

[Silvertop]

I have managed to infect my youngest sibling with a zeal for the 818 project, and he is now intent on building one. He has come across a bargain-priced 2003 Impreza TS NA 2.5 with a 4 Speed OD Automatic Transmission. The car was rear-ended by a semi, and is pretty much toast from the center door pillars back, which means that some aft components will need to be replaced. It is otherwise intact, however, and at $625, there is room for additional expenditure.

The key thing is the transmission. Little brother is missing his left foot, so being able to use an automatic transmission is critical to project viability. I am aware that you are of the opinion that in general the auto trans is something that can be easily converted to 2wd, and that other ancillary issues are resolvable.

We know that FFR is not officially supporting (at least at this time) the use of the automatic. But that does not mean that it can't be done.

Would you (and anybody else who cares to weigh in) care to comment with some detail on the viability of using this particular year and model Impreza automatic transmission? Any input you (or others) can provide will be greatly appreciated.

[wallace18]

I think as long as the kit to remove the center dif. and tailhousing fits the auto it would work. That may be the hard part. I would look to see if anyone makes a 4wd to 2wd kit for autos. The rest would be easy IMO.

[PhyrraM]

From everything I have read, it does not have the VTD tranny - which is what you want.


I would look at three possibilities:

1- Convert the existing transmission to 2WD either with a commercial kit (if available) or a DIY kit. It should only involve removing the rear drive and clutch-pack, retaining anything that also wants to come out, and cover the opening. This is likely the easiest way to keep the '03 engine ECU happy.

2- Use a pre-'96 FWD automatic transmission. They are basically the same design, but I am not well versed on the slight differences. There may be some electrical control differences that might need to be tackled to keep the engine ECU happy. This is the easiest mechanically, of course as there are no mods to make.

3- Attempt to use pre '96 FWD parts to convert the '03 tranny to 2WD. I'm *guessing* this may even turn out to be a bolt-on solution. Both mechanical and electrical compatability would have a head-start if this were indeed possible.

In any case - I'm convinced that a 4EAT 818 is not only possible, but will turn out to be relatively easy and cheap to do, once a few resourceful builders have tried it and figured out the shortcuts.

[Silvertop]

That is really helpful information. TX.

[jlahl3160]

We know that FFR is not officially supporting (at least at this time) the use of the automatic. But that does not mean that it can't be done.

I wrote several questions to FFR one was
Besides staying away fro the STI, are there other choices to avoid?

Dan Golub of FFR responed ...

The STI is the only exception when looking for a donor car, all other Impreza platforms should be able to be used.

I believed from that answer that an automatic is still a viable option. Do you have other information?

John

[Subarugears]

You can use the automatic you already have from the donor car. The Subaru automatic has a function where you can insert a fuse into one of the fuse box spots that will place the automatic trans into 2WD mode. It therefore doesn't engage the 4WD clutch pack. (Auto transmissions don't run a center differential, nor transfer gears). Then it is as simple as closing off the output to the 4WD drive shaft so oil doesn't leak out the back.

Naturally a neater way is to take off the back housing, remove all the 4WD clutch pack and then fit a 2WD housing plate.

Either will work - the first is far cheaper and easier.

[PhyrraM]

The Subaru automatic has a function where you can insert a fuse into one of the fuse box spots that will place the automatic trans into 2WD mode. It therefore doesn't engage the 4WD clutch pack. ......

This is true - but correct me if I'm wrong - using the fuse is not meant to be full time. IIRC, it holds the clutchpack duty cycle soliniod @100%. This overheats it and burns it out in a relatively short time. When it does, the transmission ECU throws a code and changes it's shift logic.

Now that I'm thinking about it again, even if you remove the clutchpack and the solinoid you would still need to install a resistor (or equivalent) in it's place to keep the tranny ECU happy.

[flytosail]

What about a hand operated clutch or something servo operated?

[Silvertop]

What about a hand operated clutch or something servo operated?

That might be an option, particularly if the automatic turned out to be not feasible. But otherwise, I think the automatic would be the first choice, based on the KISS Principle. Interesting idea, though.

[Subarugears]

This is true - but correct me if I'm wrong - using the fuse is not meant to be full time. IIRC, it holds the clutchpack duty cycle soliniod @100%. This overheats it and burns it out in a relatively short time. When it does, the transmission ECU throws a code and changes it's shift logic.

Now that I'm thinking about it again, even if you remove the clutchpack and the solinoid you would still need to install a resistor (or equivalent) in it's place to keep the tranny ECU happy.

Nope. Had a bunch of customers already do this with no problems.
You can also just not connect the drive shaft to the trans 4WD output shaft, or remove the trans 4WD output shaft.
None of it matters because the front pinion shaft (and therefore the front differential) is always fully powered.

[Subarugears]

This is true - but correct me if I'm wrong - using the fuse is not meant to be full time. IIRC, it holds the clutchpack duty cycle soliniod @100%. This overheats it and burns it out in a relatively short time. When it does, the transmission ECU throws a code and changes it's shift logic.

Now that I'm thinking about it again, even if you remove the clutchpack and the solinoid you would still need to install a resistor (or equivalent) in it's place to keep the tranny ECU happy.

Nope - had heaps of customers do it and have had no problems.
You can also just not connect anything to the 4WD driveshaft shaft, or remove that shaft alltogether.
It doesn't matter as there is always 100% drive to the front differential.
The 4WD clutch just adds drive to the rear wheels. The ECU won't throw a code.
It's beautiful. You can even go paddle shift 5 speed auto if you want.

[Subarugears]

This is true - but correct me if I'm wrong - using the fuse is not meant to be full time. IIRC, it holds the clutchpack duty cycle soliniod @100%. This overheats it and burns it out in a relatively short time. When it does, the transmission ECU throws a code and changes it's shift logic.

Now that I'm thinking about it again, even if you remove the clutchpack and the solinoid you would still need to install a resistor (or equivalent) in it's place to keep the tranny ECU happy.

Nope - had heaps of customers do it and have had no problems.
You can also just not connect anything to the 4WD driveshaft shaft, or remove that shaft alltogether.
It doesn't matter as there is always 100% drive to the front differential.
The 4WD clutch just adds drive to the rear wheels. The ECU won't throw a code.
It's beautiful. You can even go paddle shift 5 speed auto if you want.

[Grandaero]

Subarugears and PhyrraM have each contributed hugely to my understanding of the possibility of my using an automatic trans
from the 2003 Impreza that I currently have access to. Sounds like a "doable" thing so I will risk it. Worst case scenario I suppose
is that I end up with a engine to sell to another builder out here on the west coast. Thanks all !!

[Silvertop]

Note to Phyrram and Subarugears:

Grandaero is my younger recently 818-infected sibling identified in Post #1 of this thread......... :)

[PhyrraM]

......It doesn't matter as there is always 100% drive to the front differential........

For those following this, and just to be complete, this statement is only true for non-VTD auto trannies. Which is most of them.


Good to know the TCU won't bug out with missing signals, that is one area I wasn't sure about.

[BrandonDrums]

For those following this, and just to be complete, this statement is only true for non-VTD auto trannies. Which is most of them.


Good to know the TCU won't bug out with missing signals, that is one area I wasn't sure about.

My bud drove a 5mt swapped SVX for years with nearly 0 issues. They didn't touch the ECU, granted that was older electronics.

However, you can just about disable any trouble code sequence in the GD+ ecu's. If there were any trouble code to appear from unplugging/modding aspects of the automatic drive-train I think a couple check-boxes and a re-flash using ECU flash and ROM Raider would get around them.

There's also "FreeSSM" which is a little different than ECU Flash or ROM Raider but gives you full control over the TCU for Automatic Transmissons from '99 up. Electronically you can even control the % of torque split to the rear wheels so you can leave the fuse in and just change the transfer protocol to 0.

Models supported:
The software supports the models Legacy®/Liberty®/Outback®/Baja®, Impreza® (incl. WRX + STi), Forester®, Exiga® and Tribeca® starting with model year 1999 up to model year 2009.
Model year 2010 is already supported, too, but some Measuring Blocks may be missing and some Diagnostic Codes may not be displayed as plaintext.
Vehicles up to model year 1998 as well as the models SVX®, Justy®, Libero® and Vivio® are not supported.
The model years 1999+2000 must be regarded as transition period. According to present obersvations (european models), access to the engine control unit of the models Legacy®/Liberty®/Outback®/Baja® is already possible since model year 1999, while most of the Impreza®-models and a few of the Foresters® are supported from model year 2000 on.
Transmission control units are not supported before model year 2000, in most cases support starts with model year 2001.
It is useful to take a look at the diagnostic connector: if pin 7 is available, at least the engine control unit should be available.
From model year 2001 on, both control units should be supported."

A great write-up on it
http://www.subaruoutback.org/forums/65-parts-accessories-performance/39426-freessm-complete-access-your-ecm-tcu.html

The actual site
http://developer.berlios.de/projects/freessm/

[PhyrraM]

It's not just disabling trouble codes, it's making sure that the engine ECU doesn't revert to some "backup" or "failsafe" type of maps if it doesn't see the proper signals from a tranny control unit.

While I don't know the details, or really have all the skills to figure it out, I do know that (for example) all modern engines use a torque reduction strategy when the automatic transmission is shifting....I would hate to find out that the same engine (with the OEM engine ECU) has been running in this 'torque reduction' mode 100% of the time simply because it can't see the tranny ECU (even if the actual codes are suppressed).

I know some of these scenarios are far fetched, but until someone champions this and provides a solid answer you just can't be certain everything is 100%. Of course, in such a light car, less then 100% can be perfectly acceptable to some (or most?).

Interesting find on the FreeSSM, I'm gonna have to read some tonight.

[skullandbones]

I suppose this will be left up to the brave of heart to modify the autos to fit and talk with the TCU. My one auto attempt was not so good so I am a little leary of trying it without some backup. My question is: if all the above issues are solved, at least, for some generations of autos, will the mechanical fit be pretty standard? From what I have read and heard in these forums, most of the Subaru stuff mates up pretty well but the size (length) may vary quite a bit. Do the axles line up on all the same or close? Then I guess the lenth of the back of the trans will be the most critical to still fit within the 818 engine bay. Is it likely that that will be feasible or will the back of the trans have to have a bump out with some custom body work (if you don't feel like discussing it on this thread I can do a separate thread)? Thank you, WEK.

[PhyrraM]

http://farm9.staticflickr.com/8484/8250645674_266bfa546d_o.jpg (http://www.flickr.com/photos/23291496@N04/8250645674/)

From the top:

4 speed auto AWD

5 speed manual AWD

4 speed auto FWD

5 speed manual FWD

The halfshaft location is basically the same for all versions. The FWD auto looks like it will fit in the same space as a AWD 5 speed, even after the 5 speed has the tailshaft output replaced with a 2WD kit.

[bowarf]

where, or how, did you get a fwd auto?

[PhyrraM]

They were available in pre-'96 Subarus. They are of the same design as the 4EATs up to current.

[Nuul]

It's beautiful. You can even go paddle shift 5 speed auto if you want.

Can you expand on how that's done? Not that I could do it since my donor is a 5MT, just really curious how that's done.

[PhyrraM]

Can you expand on how that's done? Not that I could do it since my donor is a 5MT, just really curious how that's done.

Build a little black box that controls the transmission. By directly manipulating the hydraulic lines pressure, shift solinoids, and lockup you can simulate a manual transmission. Usually the tranny valvebody is also modified (like an 'ol school shift kit did).

[Nuul]

Neat, that sounds like a fun project in and of itself.

[Silvertop]

http://farm9.staticflickr.com/8484/8250645674_266bfa546d_o.jpg (http://www.flickr.com/photos/23291496@N04/8250645674/)

From the top:

4 speed auto AWD

5 speed manual AWD

4 speed auto FWD

5 speed manual FWD

The halfshaft location is basically the same for all versions. The FWD auto looks like it will fit in the same space as a AWD 5 speed, even after the 5 speed has the tailshaft output replaced with a 2WD kit.

Actually, what I see in those photos raises more concerns for me.

It looks like the 4 Speed Auto is 55 mm (about 2 3/8 Inches) longer than the 5 speed manual AWD before any components are removed from either unit. Will the 4 Speed auto AWD assume the same dimensions as its FWD counterpart once the rear torque converter and other unneeded pieces are removed?. And how long will a 5 Speed AWD Manual be after IT is converted to FWD? Ultimately, how much longer will the converted AWD Automatic be than its converted manual AWD counterpart? And do we know how much additional space there is on the prototypes between the end of the transmission and the coachwork?

[Erik W. Treves]

this is all cart before the horse in my opinoin...we haven't seen the final chasis and production vehicle. Anything is possible in the kit car world. FOr years they said you could use a Corvette Tranaxle in a GTM that the Porsche one was the only one short enough to work....yup...you guessed it...they put one in there...granted, they had to stretch the frame to get it in there...but it worked and it fit...

The kit is what it is...you want to color outside the lines....you need to bring skills/$$$ with that imagination to make it happen...

I recently helped complete a FF Roadster for a fellow soldier who was missing his clutch leg, but still wanted a 5-speed so his wife could jump in a drive it like a normal stick...well it took some gray matter and some $,$$$, but we finished it and he couldn't be happier. I also felt great the first time he drove down the road....I could see his smile a mile away.

[PhyrraM]

On every version of the chassis we have seen so far (IIRC), there has been nothing structural behind the transmission. This leaves only the bodywork as the limiting factor. The 5 speed transmissions will have some type of shift linkage adding to the required length, while an automatic will not.

At this point, I would feel comfortable planning for an automatic (4EAT) build. There is some risk of wasted time and money, but I see it as minimal at this time.

Of course, anything could change on the next prototype.



FWIW, I haven't seen much to prevent a STI 6 speed build either.

[Silvertop]

On every version of the chassis we have seen so far (IIRC), there has been nothing structural behind the transmission. This leaves only the bodywork as the limiting factor. The 5 speed transmissions will have some type of shift linkage adding to the required length, while an automatic will not.

At this point, I would feel comfortable planning for an automatic (4EAT) build. There is some risk of wasted time and money, but I see it as minimal at this time.

Of course, anything could change on the next prototype.



FWIW, I haven't seen much to prevent a STI 6 speed build either.

No, there doesn't appear to be anything structural behind the transmission -- just the body. In one of the gallery photos of the 818R, the entire rear cover plate of the transmission is visible through a rear body vent opening. There looks to be few inches of space between the transmission and the body, I just can't tell precisely how much. Like you I'm thinking that the chassis design is pretty much completed. It is what it is.

The hope is that little brother (I shouldn't call him that, although he's nine years younger than me, he's still 54 years old and also 6 inches taller) can get the automatic in there WITHOUT having to redesign the frame OR the body.

I'm with you -- I think it will fit. I hope so. I think he may have already purchased the donor.........

[Xusia]

We haven't seen any indications from FFR that only manual Imprezas will work. In fact, I seem to recall indications that ANY 2002-2007 Impreza will work, so long as it's not an STi. Therefore, I think 4EAT build will be fine; officially supposed even!

[Silvertop]

A couple of weeks back, my younger sibling contacted FFR with the automatic transmission question. FFR's Dan Golub wasn't at all sure that the automatic transmission would work. However, Dan's concern was whether or not the transmission could be converted to 2WD. He just didn't know. I don't think sizing was discussed. Based on that, I'm not at all sure that FFR is "officially supposing" it to fit. In fact, I think FFR has "officially" targeted only the 5-speed manual.

Should work, though.

[BrandonDrums]

It's not just disabling trouble codes, it's making sure that the engine ECU doesn't revert to some "backup" or "failsafe" type of maps if it doesn't see the proper signals from a tranny control unit.

While I don't know the details, or really have all the skills to figure it out, I do know that (for example) all modern engines use a torque reduction strategy when the automatic transmission is shifting....I would hate to find out that the same engine (with the OEM engine ECU) has been running in this 'torque reduction' mode 100% of the time simply because it can't see the tranny ECU (even if the actual codes are suppressed).

I know some of these scenarios are far fetched, but until someone champions this and provides a solid answer you just can't be certain everything is 100%. Of course, in such a light car, less then 100% can be perfectly acceptable to some (or most?).

Interesting find on the FreeSSM, I'm gonna have to read some tonight.

I don't know the details myself but I believe that disabling the codes would also disable the failsafe/limp modes associated with them. On wrx's people without much consideration of the consequences have disabled chronic mis-fire codes to keep from going to the limp mode associated with them after doing certain mods believed to cause false mis-fire readings.

As for the automatic trans, FreeSSM also allows you to change the different shift pressure and torque reduction settings for different shifting modes too. Perhaps it also gives access to change the settings on the failsafe shift modes themselves. If I'm wrong about being able to disable the failsafe sequence by disabling the codes, it would be worth looking into, that would be easier still than modding any internal solenoids and sensors to get around the issue.

Modding the failsafe would be interesting because those failsafe shifting modes on my outback are NASTY, it feels like the transmission will break itself apart the shifting is so hard. It's designed not to protect the transmission but rather to alert you that there's a problem, on my car it was just a slightly faulty throttle position sensor code but the transmission would shift so hard it literally hurt. I'd clear the code and it was back to normal.

If there is a chronic code issue that comes up by converting to 2wd, you might be able to protect the transmission from killing itself using freeSSM by making the failsafe mode normal.

I'll look into it tonight if I have time.

[Subarugears]

Build a little black box that controls the transmission. By directly manipulating the hydraulic lines pressure, shift solinoids, and lockup you can simulate a manual transmission. Usually the tranny valvebody is also modified (like an 'ol school shift kit did).

Or make it easier on yourself - simply fit the one that Subaru made. The 5EAT (same casing and size as 4EAT) in the 2005 onward Legacy GT turbo already has a paddle shift built into it from the factory.

[Subarugears]

Guys, you are overthinking this and asking questions that don't need to be asked.

Subaru made a 2WD (FWD) auto with their EJ22 cars. You can see that in the picture and measurements above from my shop floor. It would be a perfect transplant.
They also made a 4WD version of it that is exactly the same but has a 4WD clutch tacked onto the end.
You can run that in FWD mode by inserting the fuse or simply covering the tailshaft hole, or removing the 4WD clutch.
Whatever you do, the FWD part of the transmission will not be affected because it is physically connected via gears.

If you removed the 4WD transfer clutch and fitted the 2WD end plate the transmission will be just like the factory 2wd one.
And it will be the same size. So you could get the 2009 paddle shift 5 speed 4WD auto, convert to FWD and have the ultimate combo.

It will not throw any fault codes, it will not go into limp mode, it will not put your car ecu into limp mode.
The transmission ECU is not that sophisticated.

[bowarf]

If you remove the rear driveshaft and close the rear housing , or make a new back plate , what else inside the trans can be removed without affecting fwd? Are there not any bearings tthat are in the rear drive that must be retained?

[Bob_n_Cincy]

If you remove the rear driveshaft and close the rear housing , or make a new back plate , what else inside the trans can be removed without affecting fwd? Are there not any bearings tthat are in the rear drive that must be retained?

1397313974

I have never had a subaru transmission apart myself. This is what I figured out. The front diff pinion shaft is inside a hollow shaft connected to each of the output gears.
Normally the hollow shaft would drive the center diff and a spider gear in that diff would go to the front pinion shaft.
After removing the center diff. You most add a locking sleve. (see picture). This is a sleve with 2 size splines. It connects the hollow shaft to the front pinion shaft so they always turn together.
Let me know if my explaination is correct.
Bob

[rjh2pd]

1397313974

I have never had a subaru transmission apart myself. This is what I figured out. The front diff pinion shaft is inside a hollow shaft connected to each of the output gears.
Normally the hollow shaft would drive the center diff and a spider gear in that diff would go to the front pinion shaft.
After removing the center diff. You most add a locking sleve. (see picture). This is a sleve with 2 size splines. It connects the hollow shaft to the front pinion shaft so they always turn together.
Let me know if my explaination is correct.
Bob
So your saying that the shaft that is connected to the front axles goes through the shaft that is further away in the picture and then you use the second (picture) locking gear to connect the two furthest gears on the right together? that seems to make sense to me if the two gears to the right are for the center diff (one going to the front axles and one to the drive shaft).

[Bob_n_Cincy]

14009
So your saying that the shaft that is connected to the front axles goes through the shaft that is further away in the picture and then you use the second (picture) locking gear to connect the two furthest gears on the right together? that seems to make sense to me if the two gears to the right are for the center diff (one going to the front axles and one to the drive shaft).

RJH2PD I believe you got it. Calling the 2 shafts on the right gears is a little confusing. I would call them splines. In this picture i believe Parts 6,7,8,9,10 all go away. The new locking sleve, locks the blue front pinion shaft to the green driven gear shaft. The bearing that is just left of the #10 pointer is probably also not needed as the 5th driven gear is right next to a double tapered roller bearing.

I just noticed that the string was about automatic transmission. Sorry about that. I don't know if any of my info is applicable to automatics.
Bob

[Subarugears]

14009

RJH2PD I believe you got it. Calling the 2 shafts on the right gears is a little confusing. I would call them splines. In this picture i believe Parts 6,7,8,9,10 all go away. The new locking sleve, locks the blue front pinion shaft to the green driven gear shaft. The bearing that is just left of the #10 pointer is probably also not needed as the 5th driven gear is right next to a double tapered roller bearing.

I just noticed that the string was about automatic transmission. Sorry about that. I don't know if any of my info is applicable to automatics.
Bob

What you have shown in your picture and your description is the manual transmission.
It's a totally different transmission to the auto.
The auto is pretty much a regular automatic transmission.
At the back of the mainshaft - you would usually have a connection to a tailshaft and then onto the rear differential.
In the Subaru auto, you have a gear on the end of that mainshaft, this drives another gear below it, which is attached to the front pinion shaft. This front pinion shaft runs parrallel to the mainshaft and all the way back to the front, to drive the front diff. This is why there is never any loss/reduction of power to the front wheels.

Yes the rear plate has supports for a bearing on the end of each of the shafts. Hence you don't get rid of the plate.
You just get rid of the 4WD clutch or don't connect anything to it's splined output shaft.

[Oppenheimer]

Guys, you are overthinking this and asking questions that don't need to be asked.

Subaru made a 2WD (FWD) auto with their EJ22 cars. You can see that in the picture and measurements above from my shop floor. It would be a perfect transplant.
They also made a 4WD version of it that is exactly the same but has a 4WD clutch tacked onto the end.
You can run that in FWD mode by inserting the fuse or simply covering the tailshaft hole, or removing the 4WD clutch.


So the choices are use a really old 2WD Subie trans, or use the newer one from your donor and just get the rear plate off a really old 2WD Subie trans? I think the only value for these old 2WD trans are gonna be for that back plate.

[Subarugears]

So the choices are use a really old 2WD Subie trans, or use the newer one from your donor and just get the rear plate off a really old 2WD Subie trans? I think the only value for these old 2WD trans are gonna be for that back plate.

If you can get a 'really old 2WD Subie trans' then use it - it's almost exactly the same basic transmission.
I wouldn't bother with removing it from one trans and installing it on another.

[Oppenheimer]

If you can get a 'really old 2WD Subie trans' then use it - it's almost exactly the same basic transmission.
I wouldn't bother with removing it from one trans and installing it on another.

Except the old trans is old, and worn out. The donor trans is potentially low enough miles to use without rebuilding.

Will the 2WD cover fit the mentioned Legacy trans that uses paddle shifters?

[PhyrraM]

I've driven the 5EAT Legacy. Yes, it has paddle shifters. No, they are not worth using. Very slow to respond, much more waiting than fun.

Also, keep in mind that many WRXs (all?) came with the VTD automatic - which does not have the "always connected" FWD and would require a conversion sleeve similiar to the 5 speed manual. Most of the non-WRX automatics have the proper automatic (called Torque-on-Demand for many years).

[Aloha818]

Now that a few have received their kits and builds underway, any new observations on using an auto? I will be using an auto and eventually a modified version with paddle shifters. FFR is NOT supporting an auto, per email received today.

BTW, my 818 completion date is 8/31, this week YEA!

[Xusia]

Have you already bought your donor? If not, you might consider buying a newer Subaru with an EZ series H6. Those all come with automatic transmissions, AND most seem to have the manual drive mode - which looks like it would be very easy to adapt to paddle shifters.

There would be some issues, for sure: wiring harness, speedo sensor, some parts not compatible, etc.

[Aloha818]

Have you already bought your donor? If not, you might consider buying a newer Subaru with an EZ series H6. Those all come with automatic transmissions, AND most seem to have the manual drive mode - which looks like it would be very easy to adapt to paddle shifters.

There would be some issues, for sure: wiring harness, speedo sensor, some parts not compatible, etc.

Yes I have! Being in Hawaii the options for donors on island are about zero. I have a 2000 2.2l that I am adding a TD04 turbo to. Light boost, 7psi. Should be good for about 210 hp.

Transportation to Hawaii will take about three weeks, so when it gets here I can verify how much of the tail section to cut off. Then weld on a plate to block off. I guess I need to keep enough of the tail section for the bearing supports.

[PhyrraM]

Since your donor is a 2000, I would look for a '90-'95 FWD 4 speed automatic (Impreza or Legacy). There would be no need to modify the transmission and the electrics are likely close enough to be DIY with a little effort.

I would also *guess*, based on pictures, that a factory FWD transmission will fit the 818 without requiring rear bumber bodywork.

[Clif]

How much power do you think the automatics can handle?

[65 Cobra Dude]

Guys,

I pick up my kit on 9/16 and am using an 04 WRX with auto tranny. FFR asked me to make sure and document what needs to be done to make it work. I'll let you know what I find out and will be keeping a close look here as I am Subaru stupid.

Henry

[StatGSR]

How much power do you think the automatics can handle?

All of it if built right. All the fastest high horse power Subaru run automatics.

[Aloha818]

Guys,

I pick up my kit on 9/16 and am using an 04 WRX with auto tranny. FFR asked me to make sure and document what needs to be done to make it work. I'll let you know what I find out and will be keeping a close look here as I am Subaru stupid.

Henry

Have you picked up yet? Mine has made it across the Pacific and it should get to my shop today. The first item to check out is the auto trans fitment.

[Aloha818]

No one has followed up with actual information on installing an auto yet. There has been about 36ea 818's delivered so far, I guess everyone else is sticking with a stick?

I received my kit a couple weeks ago, missing the hardware, so I'm jumping around on the build. Yesterday I started on the engine install.

While I had it in the air I dropped the pan and changed the filter and gasket;
22335

With the engine on the mounts and the trans pan sitting on the frame;
22336

This shows how much of the rear needs to be cut off to fit the body;
22337

New rear trans mount will need to be fabricated, one to keep the rear section as low as possible, two because the mount location is on the section to be removed. The engine, even with the trans sitting on the frame, tips the engine slightly forward. I'm not sure if this is a problem yet. If it is then the rear frame section will need to be modified.
22338

How often does the trans need to be serviced? If maintenance or service is required the trans will have to be removed or the frame will have to be modified to gain access to the pan.

So later today I plan on pulling off the tailpiece and see if its possible to just cut off what is in the way, keep enough material to support the bearing that needs to stay and fabricate a blank off plate.

Anyone with any helpful info?

Does anyone know if its possible to lock the solenoid in its operated position without having to supply voltage via the FWD fuse? I was thinking it would be better to lock permanently so as to not have to worry about the solenoid burning up. Then if needed, add a resistor to the supply voltage to trick the ECU into thinking the solenoid is still in place.

I know others are interested in using the 4EAT, so jump in with answers, I can be the guinea pig.

[Goldwing]

I can't answer the solenoid bit, but here's the maintenance page I saved for reference to answer your maintenance frequency question. Until weather mods are made, I can see many 818s in the north needing maintenance for time not miles.
22346
22345

[riptide motorsport]

thanks for trying the auto.............................its the way I want to go.

[Aloha818]

I am not an expert, barely a shad tree mechanic, so my choice of part names, functions, and if this will work are just my observations.

Maybe too simple?

It looks to me like I just need to cut off the tailpiece section of the output shaft at the arrow in this pic;
22347

Then cut off the tailpiece housing at the arrow in this pic, which looks like it is short enough to clear the frame/bumper location;
22348

In the first pic, just before the arrow, you can see two O rings about 3/4" apart. I assume this is to minimize oil escaping to the rear of the tailpiece. In between the two O rings, in the housing, is what looks like an oil feed. So this area of the output shaft needs to stay, but beyond that looks like it can go.

Here is a pic of inside the tailpiece housing;
2234922356

So I can see what others have posted, that you have to keep the tail shaft bearing support, and then I also think you have to keep enough of the shaft and housing for the oil supply. Also, just beyond the location that the two O rings sit in, in the tailpiece, is a small hole in the bottom. Below the hole is an opening. I believe this is to let any oil that gets past the last O ring to be able to drain back into the front section of the tailpiece/transmission. So enough of the tailpiece housing must remain to keep this function.

Then only a small "plug" would be needed to cap the end of the tailpiece housing opening to keep oil from leaking out.

Not sure about the height though. With the transmission pan sitting on the frame the engine is tipped forward some, the center of the side driveshaft output is about 5" above the frame below it, anyone that has installed an engine with the 5-speed care to measure what your dimension is at this location?;
22351

Also, the height of the tailpiece housing, at the proposed cut line, is about 11" above the frame. I have not tried the rear bumper, but the flat area in this location is about 10" before it steps inward. It looks like I can cut some of the top "fin" off of the tailpiece to clear, and/or, I'm thinking that the crossbracing under trans has got to go to allow the engine/trans to sit more level, allow acces to the trans pan, and clear the bumper.

I guess I will start off with just keeping a fuse in the FWD location to keep it in FWD mode only.

[65 Cobra Dude]

Aloha,

Got your PM as well. I gave up trying to put the auto in because I could not figure out a way to not have to cut the body for the extra length of the auto. I had the FFR boys measure from the center of the CV hole on the tranny to the fiberglass body and they said it was 25 inches. I could not figure out how to keep the auto working and drop off the couple of inches needed to get it to fit without body mods. I bought a used 5 speed tranny and new clutch, pressure plate and throw out bearing and they are mounted to the motor and in the car now.

Henry

[RM1SepEx]

I am not an expert, barely a shad tree mechanic, so my choice of part names, functions, and if this will work are just my observations.

Maybe too simple?

It looks to me like I just need to cut off the tailpiece section of the output shaft at the arrow in this pic;
22347



How is this entire section attached? It appears to be similar to the center diff and output assy that we remove on the std trans. I would see if this entire assy could be removed and you could make a flat cover of some sort. Anyone have an exploded view of the auto transmission?

[PhyrraM]

http://www.northursalia.com/techdocs/pdf/transmission/4eat.pdf

While the pictures are small, pay attention to the parts related to the section labeled "MPT". The two pictures labeled "Reduction shaft seals" and "MPT power flow" show that the front axle is always powered and the rear axle (the part to remove) is only powered by the clutch - which is deactivated by the fuse.

*IF* you can determine that the shaft/gear behind the clutch is supported by a bearing (not relying on that last bearing) then you can just remove the clutch as a whole.

[RM1SepEx]

It looks to me like you could remove the whole shebang!... I'd investigate.

[Aloha818]

http://www.northursalia.com/techdocs/pdf/transmission/4eat.pdf

While the pictures are small, pay attention to the parts related to the section labeled "MPT". The two pictures labeled "Reduction shaft seals" and "MPT power flow" show that the front axle is always powered and the rear axle (the part to remove) is only powered by the clutch - which is deactivated by the fuse.

*IF* you can determine that the shaft/gear behind the clutch is supported by a bearing (not relying on that last bearing) then you can just remove the clutch as a whole.


It looks to me like you could remove the whole shebang!... I'd investigate.

Thanks guys for commenting!

My opinion, for what it's worth, is that physically the output shaft/clutch could be removed. The clutches on one end are supported by the main shaft and the back end of the output shaft has its own bearing in the tailpiece housing.

Inside bearing support in tailpiece housing.
22377

Just under the Hula Girls chin is the bearing
22379

Inside view of the clutch and the main shaft
22378

So if the clutch/output shaft is removed I believe the bearing support in the tail housing would not be required. However, it is my opinion that the outside portion of the clutch housing is part of the speed input to the transmission control unit.
There is a sensor that reads this housing;
22380

There is also a oil feed that sends oil from the trans to the tailpiece section. So if the clutch/tail shaft and housing is removed I think, again my opinion, that it will change the oil pressure and/or I would need to try and cap it.

So without any knowledge that my plan will actually work, I jumped right in and did it. I cut the tail section and output shaft as I had marked and posted yesterday.

Here is the clutch/output shaft wrapped up and ready to cut;
22381

I cut the tail section, cleaned it up and painted it like I did the rest of the trans with aluminum paint. The camera doesn't show easily but what looks like empty space just beyond the cut in shaft opening is actually the cut section of the output shaft. It is cut short of the housing by around a half inch. You can see the small hole just in from the cut that let's the oil that gets past the seals on the shaft to drain back into the trans. Both of these cut locations I think are critical, the shaft being a little short allows access to the drain hole and keeps both oil seals, and the location on the housing keeps the strengthening rib. Now I just need to fabricate a sheet metal cover plate to keep the oil from draining out. Should be no pressure here since the oil just drains back into the trans.
22389

Since this cut location gets the trans short enough to fit the 818 bumper, does not change, modify, restrict any of the bearings, seals, sensors, and oil flow, I can't see why this isn't the perfect solution! Another bonus is no extra parts/cost!
22393

So besides the cover plate, all I need is to put the fuse in to keep it in "FWD".

Comments welcome!

[nubie]

Thanks guys for commenting!

My opinion, for what it's worth, is that physically the output shaft/clutch could be removed. The clutches on one end are supported by the main shaft and the back end of the output shaft has its own bearing in the tailpiece housing.

I can't say if it is possible, but it looks like you could possibly find an open bearing, perhaps with inner race, that would fit in the 2WD tailcap and run on the end of the AWD shaft. Supporting the part that currently has needle bearings and goes inside the clutch pack. It might be necessary to remove (break or cut off) the basket on the top shaft gear (I have seen one that broke off on its own, should be doable). It would take access to a FWD tailcap to see if it is possible. That would only require a 2WD or custom back plate and another bearing mechanically. The ideal way to do it would be to pull the top shaft out and swap in the 2WD top shaft. There is a warning that the gears are a matched set and should be changed together. If there are readily available junkyards it might be possible to obtain all these pieces relatively inexpensively.



So besides the cover plate, all I need is to put the fuse in to keep it in "FWD".

Comments welcome!

I don't know if you gain anything with the FWD fuse, it will just full power the soleniod to "dis-engage" the clutch. You could just leave it, with no output shaft the drag of the fluid will be spinning the clutch pack non-stop anyway. I wonder if that rear sensor is a slip sensor for the rear wheels to determine if lock up is desired. I would just leave out the FWD fuse, minimal if any gains.

Another option is leaving the trans in full lock up AWD by unplugging the solenoid and using a proper resistor to mimic the resistance of the coil so there won't be any code from it missing. Also no real point, except simplification if you swap to a FWD top shaft.

The gears connecting the top and bottom shaft transfer power full time to the front diff, whatever previously powered the rear wheels doesn't matter, and will likely spin along with the top shaft no matter what you do with the FWD fuse or disconnecting the solenoid.

I like your cut, that is a perfect spot to make a flat plate cover. I think there are a lot of Auto donors out there and going auto is probably a simple choice for a lot of reasons (no clutch line and one less shift cable being good reasons). Watching this thread with interest.

[Xusia]

Could you just remove the clutch components of the center differential (they look like a motorcycle clutch)? That would leave the housing with race bearing intact (for support), but the RWD components would not spin.

[PhyrraM]

After looking at the pictures, I think what you did was perfect.

The FWD axle will get 100% power no matter what the RWD output does. It could spin or stay stationary without any effect on the front. You don't even need to use the FWD fuse now. Because the clutch drum has very low inertia, even if the clutch pack engages the amount of torque "taken away" from the front will be next to nothing.

Even if the computer sees a speed differential between the front sensor (on the ring gear IIRC) and the rear sensor (pictured), it will engage the clutchpack and the (now load-less) clutch drum will spin up instantly. The changes should be invisible to both the driver and the computer.

Nice job.

[Xusia]

It does look like a really nice job. It kinda cracks me up that you call yourself a shade tree mechanic! Your work thus far looks excellent!

[Aloha818]

Thanks PhyttaM, Xusia, Nubie, and RM1SepEx for your time to reply and comments!

AZPete replied to the question about the distance from frame to the center of the side driveshafts in my build thread, his pic is from a 2006 5MT in 818S;
22413

This is almost exactly what I have with the trans pan sitting directly on the frame. So I guess I'm going to leave the frame under the trans pan intact. When the trans mount bushings arrive (for a BMW) I will build the height to be about 1/4" space, then raise as needed to keep the pan from contacting the frame under load. I also plan on adding adding a brace to the top of the engine to keep it stable.

[RM1SepEx]

That distance doesn't really matter, the CV joint can deal with any misalignment easily

[Aloha818]

That distance doesn't really matter, the CV joint can deal with any misalignment easily

Dan thanks for commenting.

I believe that the CV joint can handle some misalignment, as that is its purpose to move with the suspension travel. My main question in asking the measurement from a 5-speed transaxle is for a point of reference, as is my cast the engine assembly looks like it is too far tipped forward. The output shaft location is somewhat close to center and the engine mounts are just a little forward. My guess is that for every inch the rear of the trans is high the output shaft height will be about 1/4" high.

I set the bumper on to check orientation. Looks pretty good, but higher that what I've seen as the tail location on the 5-speeds;
22436

Since I want as much room over the rear of the trans for exhaust and maybe a little storage, and then I'm concerned about the tilt of the engine and access to the trans pan, Im going to go ahead and rework the 1" square bracing under the trans and let the rear drop down about an 1 1/4".

I'll update as I make the changes.

[riptide motorsport]

Nice avatar, shaaawing................:p

[Aloha818]

Nice avatar, shaaawing................:p

Thanks! Gotta show Hawaiian Spirit right?

Today I finished modifying the rear section of the frame for the auto. For better or worse I felt that access to the pan and getting the engine/trans a little more level was more important that the cross bracing I had to remove;

2253722538

Then I welded in another 1" tube between the rear lower control arms, and flipped the existing rear trans mount plate, I'm hoping enough steel to make up for what I removed. I'm not a great, or even good welder, but good enough to get it done. Then primed and painted;

2253922544

I made a rear transmission mount from a piece of 1" angle and a new pair of transmission mounts that are for a BMW;

22540

The bottom of the trans pan is now about 1/2" above the bottom of the frame;

22541

And the center of the side driveshaft location is still close to 5", which is about the same as the 5-speed;

22542

And now the engine sits a little more level and the trans pan is fully accessible and the trans mounts should help stabilize the rear and still minimize vibration;

22543

[Wayne Presley]

I'm no so sure I would have taken the bracing out which supports the rear suspension when you could take off the rear mount and tilt the motor forward enough to remove the pan. You can remove the trans in less than an hour if needed, even on a completed car.

[Aloha818]

I'm no so sure I would have taken the bracing out which supports the rear suspension when you could take off the rear mount and tilt the motor forward enough to remove the pan. You can remove the trans in less than an hour if needed, even on a completed car.

Wayne, thanks for commenting. I should have mentioned I am adding a solid steel plate, bolted/removable from the bottom, to take the place of the cross bracing. Also, besides making the trans pan accessible, I needed to drop the rear of the trans into the area of the cross bracing and have room for the trans mounts.

[Wayne Presley]

Wayne, thanks for commenting. I should have mentioned I am adding a solid steel plate, bolted/removable from the bottom, to take the place of the cross bracing. Also, besides making the trans pan accessible, I needed to drop the rear of the trans into the area of the cross bracing and have room for the trans mounts.

I'd bolt in 8 per side and you are going to need to put sleeves in the tubes to keep the bolts from crushing the tubes. All and all I think it would be easier to have kept the X brace for the number of times the trans pan will need to be removed.

[Aloha818]

It's taken me a little time to get here, but I can report that a 4EAT auto will fit in the 818.

I took my first test drive today. I'm in a city environment so I can't really get up to highway speeds until I have it registered. I did get up to 45 mph with no issues.

Since the stock shifter cable will obviously not reach I bought a PCS Push Button Shifter. Works perfectly.

[Wayne Presley]

Does the ECU control the shifts or is the trans self contained?

[Bob_n_Cincy]

Does the ECU control the shifts or is the trans self contained?

The TCM in the 06 does all the shifting. This is out of the 06 manual.
27668
27669
27670

[Aloha818]

Does the ECU control the shifts or is the trans self contained?

Wayne, I'm using the stock 2000 ECU and stock 2000 TCU. The PCS push button shifter just moves the stock linkage location from driver input/selection.

[Aloha818]

Since its been about two years (can't believe it's been that long ago) and I have more experience with my build using the 4eat, I thought I should give an update.

My previous comments about the mechanical modifications remain unchanged. Both the engine and the transmission were both operating on their stock ECU/TCU's.

After my first build completion and driving in October 2015 the trans ran and shifted as you would expect in a stock Subaru. After my first days of actual driving I made a list of things I wanted to change and put the car back in my shop and went back to work. I did not have any changes related to the trans on the list.

What was on my list was a complete rewire of the car including the engine harness, to get rid of all the Subaru harnesses and starts fresh with a generic harness from Painless and the harness from Haltech to go with the new ECU.

During my rewiring stage I asked advice from Level 10, PCS (Powertrain Control Solutions), IPT trans, and lots of reading on several forums about how to control the 4eat with an aftermarket ECU. All said it either couldn't be done, and/or they didn't offer control solutions. My local tech, John, from Hawaii Performance disagreed. He said for me to use the stock TCU, feed it power, ground, brake light and TPS inputs and it would work. I also have the front wheel drive "fuse" connected and the dropping resistor connected.

I've driven the car now about a hundred miles, at least 10 WOT from stop through all four gears, and 3 hours on the dyno with 9 full pulls. No hiccups yet. Shifts smooth and predictable in stop and go traffic, and snaps through the gears at WOT, even got a little bark from first to second.

It is a little different sound than manual shifting with turbo's, no unspooling/spooling at each gear change.

My first SCCA event will be April 3rd. I'll update again sometime after that with more observations.

[turbomacncheese]

Glad to hear this is working out. I'm looking at an auto build for my daily driver, and traffic on the 101 outside Phoenix is just...stupid. I'd really love to hear more about your experience, and any performance measurements you have.

Thanks.

[JB91710]

The Porsche 917/10 Can Am Car Replica I built has a 2007 Tribeca EZ30 and the Sport Shift 5eat. Actually, it has two EZ30 engines but that's another wiring/management nightmare. I have heard about the fuse business and hope that works. I was wondering if all that stuff in the back of the transmission can be removed and a plate attached to cover the end. I also wonder, will some kind of retainer be necessary to hold other guts in place.

5758757588575895759057591

[maclonchas]

Aloha818,

I know it has been a while since you posted on this thread, but I was wondering if you have any pictures of the back plate you made for the 4AT. I followed all your steps in the thread, but this was the only picture missing.

Thanks


Bill

Since its been about two years (can't believe it's been that long ago) and I have more experience with my build using the 4eat, I thought I should give an update.

My previous comments about the mechanical modifications remain unchanged. Both the engine and the transmission were both operating on their stock ECU/TCU's.

After my first build completion and driving in October 2015 the trans ran and shifted as you would expect in a stock Subaru. After my first days of actual driving I made a list of things I wanted to change and put the car back in my shop and went back to work. I did not have any changes related to the trans on the list.

What was on my list was a complete rewire of the car including the engine harness, to get rid of all the Subaru harnesses and starts fresh with a generic harness from Painless and the harness from Haltech to go with the new ECU.

During my rewiring stage I asked advice from Level 10, PCS (Powertrain Control Solutions), IPT trans, and lots of reading on several forums about how to control the 4eat with an aftermarket ECU. All said it either couldn't be done, and/or they didn't offer control solutions. My local tech, John, from Hawaii Performance disagreed. He said for me to use the stock TCU, feed it power, ground, brake light and TPS inputs and it would work. I also have the front wheel drive "fuse" connected and the dropping resistor connected.

I've driven the car now about a hundred miles, at least 10 WOT from stop through all four gears, and 3 hours on the dyno with 9 full pulls. No hiccups yet. Shifts smooth and predictable in stop and go traffic, and snaps through the gears at WOT, even got a little bark from first to second.

It is a little different sound than manual shifting with turbo's, no unspooling/spooling at each gear change.

My first SCCA event will be April 3rd. I'll update again sometime after that with more observations.