.64 or .82 OD TKO 600?

[aarvig]

Boy, I'm seeing a lot of opinions on this. My set up is Dart 427 with 560 horse and 560 Tq, 3.50 rear end gears and 25.68 inch tires. The calculators are showing 2150 rpm at 70 mph in 5th for the .64 and 2650 rpm at 70 in 5th for the .82.
The engine builder has reassured me this engine will not lug from 1900 rpm's and up. I'll be doing a lot of back road cruising with the occasional highway run. Which way would you guys go?

[Mark Dougherty]

.64 for the street

[Bob Cowan]

I have the .64 gear. There's about a 1,000 rpm drop from 4th to 5th. On the highway cruising along at 80mph the OD is great. But on the back roads, I find myself in 4th a lot, simply because there's no in between.

[aarvig]

.64 for the street

Thanks for the advice. Hmmm, travelling builder? I have a feeling we will be meeting at some point in the future.:D

[NukeMMC]

Thanks for the advice. Hmmm, travelling builder? I have a feeling we will be meeting at some point in the future.:D

You won't regret that decision.

[2bking]

As one who just converted my transmission from .82 to .64, I can agree with Mark. The .82 ratio just had too many RPMs when on the highway and caused a lot of exhaust noise. I have the Coyote engine and run 5th gear at 1000 RPMs which is about 30 MPH in my roadster. The Coyote pulls very smoothly at low RPMs.

[boat737]

I have a nearly identical setup in process. (427 Dart, TKO 600, Ford 9 inch, 3.5:1, although I do have a slightly milder cam) I don't have it built or running yet, but I do have the .82 sitting in the garage. I don't plan on doing any cross country treks with it, more of an around town and daily driver. I'll know if it's the right choice in a year.

[GoDadGo]

Are there many or even any 6-Speed options out there for the Ford power plant that would allow the use of the solid axle or are you guys stuck with running 5-Speeds?
I've been able to stuff a ZF S6-40 in my 383 SBC powered MK-4, with a Moser TSD 3/Link, but stuff had to move around a pretty good bit.
Could the T56 be adapted to fit or is to long to install without going with the independent rear?

[edwardb]

6-speed options mainly only work with an IRS setup due to the longer transmission and resulting shorter driveshaft. A solid axle setup -- where the diff needs to move -- just doesn't work well with the really short driveshaft. To the OP, I've had both. .64 and .82 TKO 600. I like that with the .82 there's less of a gap between 4th and 5th, and it becomes a usable gear other than just a highway overdrive one. Like Bob mentioned. But on balance I like the .64 better. For street driving 4th is just fine for up to (and exceeding...) normal speed limits and the OD 5th provides a better and more comfortable highway cruise. My current build with a Coyote and 3.55 diff is the .64 TKO.

[GoDadGo]

Hey EdwardB,

I knew that you'd know the answer.

For the record, I had to move my entire driveline forward in order to clear the distributor to get the ZF's shifter in the right spot. I also moved the engine and transmission to the left a bit so it is inline with the pinion. The good news is that my drive shaft is actually straight, from a left to right perspective, plus it is a couple of inches longer, about 13", so I'm able to run the 3-Link solid axel.

Would it be possible to do the same with the Ford and T-5/6 application or is that transmission just too long?

Thanks,

Steve >> aka: GoDadGo

PS: I'll be turning around 1,750 RPM's at 70 MPH according to your RPM calculator so good gas mileage may be possible.

[CDXXVII]

I have the .82 and so far no issues with noise or high revving. For the type of driving you are describing I think the .82 would be just fine. I have heard lots of comments about the noise at higher rpm levels and I do not find this to be an issue. I use ear plugs most of the time due to wind noise and not exhaust. I am running the Gas-N pipes and my engine sounds really good at higher rpm's. I am running the Ford Racing Z427 with 3.31 rear end for reference. My friend has a 600HP 427 with the same setup less the Gas-N pipes and we spent a couple hours on the freeway to the Huntington Beach event two years in a row and never thought the .82 revved too high. I really like the fact that the gears are evenly spaced and you do not deal with the large gap between 4th and 5th for the OD version. Might be nice to lug along on the freeway at 1700 rpm's for fuel economy but that was never my intent.


I'll be doing a lot of back road cruising with the occasional highway run.

[GoDadGo]

My 5th gear is .75 and 6th is .50. so I get the even spacing of the overdrives.

[CraigS]

I think you might be better off w/ the .82. By your calculator w/ the .6 at 70 you are only 200 rpm over your minimum, so every time you drop down to 60, you will need 4th. In your 'lot of back roads and occasional highway' use you will really notice the somewhat un-natural gap from 4th to 5th. OTOH, can you go one step milder on the cam lose 20(?) hp at 6000 rpm, gain some low end drivability, and use the .64? Overall, for me anyway, an engine that isn't comfortable below 1900 wouldn't be very enjoyable. W/ 427 cubes and a 2500# car, you really don't need a peaky engine

[edwardb]

Hey EdwardB,

I knew that you'd know the answer.

For the record, I had to move my entire driveline forward in order to clear the distributor to get the ZF's shifter in the right spot. I also moved the engine and transmission to the left a bit so it is inline with the pinion. The good news is that my drive shaft is actually straight, from a left to right perspective, plus it is a couple of inches longer, about 13", so I'm able to run the 3-Link solid axel.

Would it be possible to do the same with the Ford and T-5/6 application or is that transmission just too long?

Thanks,

Steve >> aka: GoDadGo

PS: I'll be turning around 1,750 RPM's at 70 MPH according to your RPM calculator so good gas mileage may be possible.

Moving the engine forward from the stock location has a number of potential issues. (1) Standard headers no longer fit. The side exhaust cutouts are already right at the back edge of the wheel well. No wiggle room there. (2) Interference of the crank pulley with the 4-inch frame cross member. (3) Interference of the engine and/or accessories with the steering column. (4) Transmission frame likely would need to be modified or moved. (5) Upsetting the nearly perfect 50/50 front/back weight distribution. That doesn't include the effort to remove the existing motor mounts and relocate/weld to a new location. Other than that it's a great idea. :p

I'm not quite following moving the driveline to the left either. Whether IRS or solid, diffs typically have the ring gear in the center and the pinion slightly to the right. That's why the Roadster (and basically all rear wheel cars) have the driveline favored to the passenger side. Well passenger side with left hand drive. With the standard FF layout, the driveshaft is dead straight in the chassis from the trans tailshaft to the diff with the driveline offset as mfg'd.

Note these comments are for the various Ford engine options, the most common. I don't have personal knowledge of non-Ford engine options.

[GoDadGo]

Yes I know that the engine is mounted longitudinally, but the fact of the matter is when you make a one size fits every Ford V/8 known to man kit car, you've got to make compromises, lots of them.
While I must admit that my build has a ton of "One Off Changes" I think I'll really enjoy the final product in the end.
I just wish you guys had more transmission choices and additional gear ratio options.
Slightly better, less severe, drive shaft angles would be a big plus too.

[rich grsc]

I think you might be better off w/ the .82. By your calculator w/ the .6 at 70 you are only 200 rpm over your minimum, so every time you drop down to 60, you will need 4th. In your 'lot of back roads and occasional highway' use you will really notice the somewhat un-natural gap from 4th to 5th. OTOH, can you go one step milder on the cam lose 20(?) hp at 6000 rpm, gain some low end drivability, and use the .64? Overall, for me anyway, an engine that isn't comfortable below 1900 wouldn't be very enjoyable. W/ 427 cubes and a 2500# car, you really don't need a peaky engine
No I don't think that would be necessary with a big block 560hp and 560tq.
I have a near stock sbf, and I can easily drive at 50mph in 5th. The slower you can turn the engine at highway speeds, the more pleasant the ride.

[edwardb]

Yes I know that the engine is mounted longitudinally, but the fact of the matter is when you make a one size fits every Ford V/8 known to man kit car, you've got to make compromises, lots of them.
While I must admit that my build has a ton of "One Off Changes" I think I'll really enjoy the final product in the end.
I just wish you guys had more transmission choices and additional gear ratio options.
Slightly better, less severe, drive shaft angles would be a big plus too.

I don't know what compromises you're speaking of when the build is within the stated design parameters. But the debate doesn't matter. Given enough time, money, skill, etc. pretty much anything can be done. And it probably has. The important thing is you're building your car the way you want it, and I'm sure you will enjoy it. I'm not going to say or do anything to take away from that. Knock yourself out! :)

Regarding gear ratios in general, IMO the subject is probably a bit overthought and over analyzed. Take a look at the available OD ratios and target speed/RPM for that gear and that about covers it. These things are so light and highly powered there almost aren't bad choices. Any of them will probably perform more than we're personally capable. Of course there are exceptions, but for most of us and our street cruising they all work quite well.

[GoDadGo]

I don't know what compromises you're speaking of when the build is within the stated design parameters. But the debate doesn't matter. Given enough time, money, skill, etc. pretty much anything can be done. And it probably has. The important thing is you're building your car the way you want it, and I'm sure you will enjoy it. I'm not going to say or do anything to take away from that. Knock yourself out! :)

Regarding gear ratios in general, IMO the subject is probably a bit overthought and over analyzed. Take a look at the available OD ratios and target speed/RPM for that gear and that about covers it. These things are so light and highly powered there almost aren't bad choices. Any of them will probably perform more than we're personally capable. Of course there are exceptions, but for most of us and our street cruising they all work quite well.

As Always You Make Excellent Points Sir EdwardB!

Before becoming a Banker, I studied Naval Architecture and Marine Engineering at the University of New Orleans. My engineering background causes me to over think everything, especially the mechanical world.
To this day things like shaft angles, centers of gravity, still water bending moments, side heel wind loads, still bounce around my brain.

That's why little things like U-Joint angles and wide spread ratios keeps me up at night.

[aarvig]

I appreciate all the replies guys. I think I'm going to stay w/the .64. This motor has A LOT of torque. I don't mind downshifting but I know my wife and I will be bothered by loud highway RPM's. Edwardb, thanks a lot for your input on your preference. It helped settle my decision.