2019 irs 3.73

[Brandonk603]

Hi Everyone,
Im in the early stages of planning a build for a Daytona Coupe. I bought a 351 Windsor and going with a TremecT56. As far as the IRS I have my eyes on 2019 complete assembly wit 3.73 gears. It also comes with brakes, rotors, spindles, ect. The entire assembly. Its $1200 plus shipping. This is my first build so Im trying not to make any major costly mistakes. With that said Im somewhat disappointed with the lack of detail Im getting from tech support. Im sure they are swamped with orders so I dont want to give them a hard time. They may also get frustrated with guys ike me that are not very knowledgeable about buiding cars!:rolleyes: I have many questions about the complete kit. When I hear complete kit I was thinking I just needed an engine, transmission, and differential. But it looks I will need brakes and other miscellaneous parts? Im also trying to get an answer on whether or not I get a credit on any parts I dont need at the time of the order. I realize I havent ordered the kit yet but again I dont want to make any major mistakes. Am I wasting my money buying an entire used assembly or is it cost effective?
You guys were already very helpful with answering my questions on the transmission and really do appreciate it!

Brandon

[Gordon Levy]

Whether you are wasting money on the complete kit is a matter of opinion and what you are building for a car. I personally buy base kit plus any options I want from FFR. I have my own line of parts such as brakes, fuel systems, drivetrain and a host of other parts that I use in my builds. Trying to delete parts from the complete kit from FFR is not worthwhile, they don't want to for one and if they did the credit isn't worthwhile. The 3:73 torsen IRS in a nice piece and works well. If you want to talk at length feel free to call me.

[P100DHG]

1. 351 + T56 + IRS= custom driver shaft. Factory five doesn’t have a driveshaft for this combo (at least when I ordered) TKO600 basically is going to give you the same gearing. You’re basically shifting from 4th to 6th and missing 5th on the TKO. I have a 6 speed Porsche and 5th is useless. It’s extra aggravation you can do without. You’ll be aggravated enough trying to stuff that 351 under the hood without body modifications. I just squeezed mine in barely Jeff Miller (the guru of body and paint of these cars) and I were talking about it today actually.

You WILL get credit on parts you don’t need. I took a sizable credit on seats and the center section.

I highly suggest reading my build thread. I started this knowing literally nothing about cars. It’s all there. I directly address the IRS kit. Mine has a 3.73 from a former mustang it’s actually how the thread starts. You need to order 16668 - 2018 Mustang IRS 3.55 Center Section, Spindles, and Hubs from FFR. Then delete the 3.55 center section from this package. FFR gave me $1000 credit and I got my 3.73 center section for $375. It the only “something borrowed” part on my car.

I think new builders can learn a lot from my journey and my journey is still unfolding. Just click around on the table of contents if you want to jump around. If you’ve got questions let me know and I’ll try to answer them on this thread.

https://thefactoryfiveforum.com/showthread.php?29393-P100DHG-Build-Thread

[edwardb]

A complete kit has everything except engine (including bell housing, flywheel, clutch), transmission, rear axle or center section (IRS), rear brakes, wheels, and tires. Basically what you said. Add those parts and you have a running/driving car. That's the idea. Depending on rear suspension choice (IRS or solid axle) you'll need the appropriate parts to complete. Also what you said. The complete kit is set up for a basic carb installation. So if you do EFI, for example, you would need the added electric fuel pump, wiring, etc. If you want heat and A/C, an option. Side windows? An option. Insulation? An option. All of this becomes pretty apparent if you study the website and also the order form.

Not to complicate the issue too much, but some do order the basic kit and then add the additional parts via their own selection versus what's offered by Factory Five. I've done it a couple times myself. Many assume the basic kit is only for donor builds. That's not necessarily the case. But it's really not a way to save money. Many have proven that. But I wouldn't recommend this approach if you aren't experienced.

Factory Five will give you credit if you want to delete parts from the kit. They didn't used to, but over the last several years they've become more flexible about it. The only thing is the credits offered are pretty low. Maybe at their cost? But I don't know. For some items, you'll get more by taking them with the kit and selling the unused parts to other builders. If it's something others can use (like seats, etc.) you can usually get 50-60% of retail. Often more than the credit. But it's a hassle you'll have to decide if worth it.

Going to have to disagree with P100DGH on the characterization between the TKO and T-56. A T-56 is not just a TKO with an added overdrive gear.

TKO: 1st: 2.87, 2nd: 1.89, 3rd: 1.28, 4th: 1.00, 5th: 0.64
T-56: 1st: 2.66, 2nd: 1.78, 3rd: 1.30, 4th: 1.00, 5th: .80, 6th: .63

First through third are actually quite different. If you run the numbers on a calculator (like this one https://www.tremec.com/calculadora.php) you can see first through third with the TKO and 3.55 is very similar to the T-56 and 3.73. It’s not just theory. I had the TKO/3.55 in a Roadster and the T-56/3.73 in my current Coupe. Fourth and up they’re about the same, and the 3.73 will give you a slightly higher RPM at cruise. But it’s not objectionable. Also, I find the .80 “in-between” overdrive of the T-56 very nice as it reduces the gap between fourth and fifth like in the TKO. For cruising speeds less than 70+ on the highway, like 50-55 mph 2-lane highways all around where I live, fifth in the T-56 is perfect.

A lot of words to say I think the T-56 and 3.73 combination is a nice one. Plus the fact that the 3.73 is a Torsen setup makes it even more desirable. Sounds like you have a good deal there if in good shape. I bought my 3.73 center section NIB. So it cost a little more than that. :rolleyes:

One other point. As you're doing your research, you'll probably find that Tremec has replaced the TKO with the newly released TKX. Looks like everything is the same for mounting, spline counts, dimensions, ratios, etc. Just a bunch of improvements that look good.

My Gen 3 build thread and a video are in my sig line below. It’s done and I was able to drive almost 2,000 miles this past season. Absolutely love it. Good luck with yours.

[P100DHG]

The more variables you add to the build the harder it becomes to finish. Big picture is that T56 + 351 + IRS is over complicating this for a new builder. I mean where is the shifter going to land? What if it’s outside of the precut transmission tunnel panel? Then it’s sheet metal work. Then you’ve got measuring and cutting the drive shaft, shortening rewelding and balancing.... then it’s managing intake manifold height and air filter or body modifications.

Seems overwhelming to me.

TKO + midshift + 351 + IRS is a drop in solution with the right air cleaner and intake manifold.

[edwardb]

The more variables you add to the build the harder it becomes to finish. Big picture is that T56 + 351 + IRS is over complicating this for a new builder. I mean where is the shifter going to land? What if it’s outside of the precut transmission tunnel panel? Then it’s sheet metal work. Then you’ve got measuring and cutting the drive shaft, shortening rewelding and balancing.... then it’s managing intake manifold height and air filter or body modifications.

Seems overwhelming to me.

TKO + midshift + 351 + IRS is a drop in solution with the right air cleaner and intake manifold.

I don't like to argue on the forums, and generally just walk away and let the OP decide about the advice given. But just not sure where you're coming from here. The 351+T-56+IRS is a drop-in option. As with any 351 installation, some care necessary to pick the right intake, etc.. But nothing out of the ordinary. Certainly no different because of the transmission. The T-56 shifter will be in the right position by just flipping around the rear location. No midshift required, which is not a simple or inexpensive mod. Factory Five now offers a driveshaft for this combination. Part number 60450 on the order form. In multiple builds, I've never had the cut-out on the transmission tunnel cover that was in the right location. I wish they'd leave it uncut. Whatever, super easy to rivet on a filler and put he hole where it needs to be. My advice? Pick your transmission based on the merits of each and whichever best fits your build plan and goals. But for the Coupe, one is not particularly more complicated than the other.

https://hosting.photobucket.com/images/ab234/edwardb123/IMG_0286.jpg?width=590&height=370&fit=bounds (https://app.photobucket.com/u/edwardb123/a/186cc666-68d0-4881-b53c-af005ffe3552/p/ddb3499c-d4a9-455a-86b5-4c44ff851726)

[Brandonk603]

I am looking for the first build to go somewhat smooth and not get into cutting the frame or modifying panels. One of my questions to you guys earlier last month was what transmission would be best for ease of install and not over complicating things and it sounded as if T56 was the best option as far as gearing and install but I may have not provided enough information on engine and IRS. At this point changing engines is not an option as Ive already purchased a 351W and having work done to it as we speak. I know Im limited to the Edelbrock Performer intake due to height limitations but wasnt aware if I use a 2019 IRS I cant use the T56 without a custom driveshaft. Also I was told the TKO would not be an easy option on the install without modifications. Im not expecting this build to go like putting together a new piece of furniture nor do I want it to as Im really looking foward to the whole build process. I have my wife and 2 daughters who are all on board with helping which makes it even better.
Thanks again guys your all very valuable!
Brandon

[edwardb]

I am looking for the first build to go somewhat smooth and not get into cutting the frame or modifying panels. One of my questions to you guys earlier last month was what transmission would be best for ease of install and not over complicating things and it sounded as if T56 was the best option as far as gearing and install but I may have not provided enough information on engine and IRS. At this point changing engines is not an option as Ive already purchased a 351W and having work done to it as we speak. I know Im limited to the Edelbrock Performer intake due to height limitations but wasnt aware if I use a 2019 IRS I cant use the T56 without a custom driveshaft. Also I was told the TKO would not be an easy option on the install without modifications. Im not expecting this build to go like putting together a new piece of furniture nor do I want it to as Im really looking foward to the whole build process. I have my wife and 2 daughters who are all on board with helping which makes it even better.
Thanks again guys your all very valuable!
Brandon

I don't think anyone suggested you have to use a different engine. I certainly didn't. As long as you're aware of the height issue (sounds like you are) then you'll be fine. Either transmission (TKO/TKX or T-56) will fit into the Gen 3 Coupe without modification. Factory Five now offers a driveshaft for either combination, including the SBF/T-56/IRS (60450 - 31 spline driveshaft for 302/351W with T-56 Magnum transmission) as I mentioned. So shouldn't be anything to do there. The only uncertainty IMO is where the shifter falls. Every build has to deal with this and sometimes it's not predicable. Or sometimes where it does work isn't an angle the builder wants or expects. The picture I posted is my Gen 3 Coupe with a Coyote and T-56. The only thing necessary was to flip the rear shifter location around (six bolts in and out) and it cleared the frame cross member plus was in a nearly perfect location for me. Your SBF is slightly longer than a Coyote (about 1 inch) so the shifter would be back slightly from my picture. But still should clear and still work just fine.

Two other comments about the T-56 in addition to the previous comments I made about the ratios and the added overdrive gear. (1) Having had both, the T-56 clearly shifts better than the TKO. A lot better. So that's a definite plus. Now having said that, if you end up with the newer TKX, it's supposed to have addressed these issues so I'd expect the two to be very similar. (2) The T-56 does have the reverse gear solenoid lockout. It's a very nice feature that I like a lot. But does have to be addressed. Not a big deal, just reminding about it for full disclosure. I talked about it at some length in my build thread, how to address, and what I did.

I've installed TKO's in Roadsters but not in the Coupe. So I can't give specifics about where the shifter would fall and what if any modifications are required. But most do use the midshift as P100DHG mentioned. That's something you would likely need to order along with the transmission since it involves opening the case and doing some part swaps. Not something most builders attempt.

It's very likely with either transmission the cutout in the transmission tunnel won't be exactly right. You may need to add a blocking plate and re-locate the hole. Not hard at all. These builds will have lots of "challenges" that you need to work through. Usually simple enough and the Factory Five tech support and this forum (along with the manual of course) are available to assist. But some may be a little more difficult. You need to be prepared for that and not let it derail you. Every one of these are custom builds. They're not snap together kits. Not everything can be predicted or prevented. You deal with it when it happens. Sorry if that sounds a little preachy. But I see newcomers get discouraged or even very negative when stuff happens. Which it will. These are a blast. Not only the build part, which I truly enjoy, but also the final product. But it's a journey with lots of discovery and learning along the way.

I'm sticking with the advice I gave before. Choose your transmission on the merit of which best fits your build plans and expectations. Either will work with similar effort. Don't overcomplicate it. Good luck.

[P100DHG]

Factory Five now offers a driveshaft for either combination, including the SBF/T-56/IRS (60450 - 31 spline driveshaft for 302/351W with T-56 Magnum transmission) as I mentioned. So shouldn't be anything to do there. The only uncertainty IMO is where the shifter falls.
This is great info thanks for sharing. Glad to see they are improving their options.