MPD47

There is a 944 with a C5 transaxle in it. I considered except it's banned from PCA club racing. Rogue, if you're flat shifting I have ZERO sympathy for you.

KuHL 951

I see what you mean, the outputs are really far to the rear. It would probably require cutting up the hump between the rear seats. It does look like maybe the rear TT/TA coupling housing is a bit smaller diameter than the 951 though, just longer overall. How is manual shifting done on the C5, I know nothing about them?

333pg333

There has been some pictures posted on a thread here of a guy who did exactly that and changed out the entire tranny and suspension setup to a Corvette. It was done very well and this guy had a big V8 up front, probably an LS1 (Steve something rings a bell?) I guess this is the guy that Mike is referring to. Not sure on specifics but it looked very impressive. Anyone remember this???

Rogue_Ant

My flat-shifting was developed by ST. There is no power-shifting going on. Perhaps you should look at the link in my sig. Besides I'm not asking for your sympathy.


-Rogue

333pg333

I have been doing a bit of digging and this is a reply I got elsewhere in regards to the 931 box and why in fact he believes it's the strongest of all the front engined/rear tranny options. This guy has done a fair bit of research I might add so it's not just bench race facts.

"There is a very basic design reason for the G31 to be stronger. The ring and pinion, differential and bearings are significantly larger in both diameter and tooth size. The tooth length, width and contact area of the ring and pinion are grossly larger and the training pitch of the teeth is a lessor angle. Meaning there is more tooth contact along with more material to each tooth to carry loading. The angle of the teeth on the rest of the gearing is also at a slightly lessor angle which translates into a stronger tooth design. There are two bearings on each end of the pinion and mainshaft (one roller and one cylinder roller and one 4 point roller bearing) to distribute the load where the AUDI design has only one. On the AUDI (016/083) design the pinion uses one tapered bearing on each end and the mainshaft uses one smaller ball bearing, one roller and a small needle bearing to support the load. The differential side bearings on the G31 have about 1.5x the load capacity as the 016/083 based on bearing manufacture specs. The output stub shafts are also much larger on the G31.

The 968 transaxle (01E) is essentially comparable to the 944 turbo but not the turbo S. It shares the larger ring gear and front pinion bearing. It is not as strong as the 2nd version of the AUDI 01E. It does not have the wider first gear and updates on 3rd gear. The turbo S transaxle has shot peened gears and shafts which add to reliability, impact and torsional strength.

The most common G50 is not as desirable as the later updated version and much less desirable to the turbo version due to the smaller ring gear. The most common version has the same size ring and pinion as the 944 turbo and 928 transaxles. The updated version has a larger ring gear and the turbo version has a ring gear as large as the G31."

Makes interesting reading. Wonder how possible it would be to convert?

SoloRacer

Out of curiosity, does anyone know what - if any - the differences are between the 951 Turbo S tranny and the Rothmans Cup tranny are? I bought Rage's old car and it has a Rothmans Cup tranny in it.

Rogue_Ant

Convert to which transmission?


-Rogue

333pg333

The 931^. I'm not sure on the finer intricacies of how you'd put one in place of the other. I'm not saying that it is definitely the answer either. I want to read a bit more into it. Scott Gomes is happy enough with our trannys and says that he's had well over what power levels we're talking about.

DVC

Here is Steve's C5 trans swap (C5 Corvette torque tube, transaxle and entire rear tranny/suspension cradle, C5 Corvette dual rear A-Arm suspension):



When I asked him about it: "It wouldn't be too practical for a street car, as I don't think it's possible with the stock fuel tank. Since we're running a fuel cell and relocating it, we had more space. That'd be the biggest issue."

DFASTEST951

Hey, I just read through this. I have a little insight based on my research over the last year.

I have the 89 Turbo S Transaxle with the shot peened gears and shafts with the motorsport LSD. Well, most of you know I broke second gear.

The 968 01E six speed is much stronger than the 951. David Raines, Scott Gomes, Chris Cervelli, Eric Johnson (Carquip), Roger Brown (Powerhaus II), and many other builders have the experience first hand to know this..

That said, if you want to stick with the five speed, the 89 Turbo S is the way to go. What we don't realize is that many of us are putting out more than double the factory hp and tq so it"s no surprise to me when it breaks. The fix? Stay with the 89 Turbo S, have the gears cryogenically treated, and most of you should be in good shape. To be sure, a taller ring and pinion would put much less stress on the whole box and let us utilize our powerband more. Ultimately making our big power cars less prone to break and even faster. Custom r&p is $3,200 and trust me, that's the very best price you are gonna get without a group buy.

If you go the six speed. Much stronger. A new r&p is almost necessary as the six gears top out at almost the same speed as the five speed. So a taller r&p will not only destress the already stronger box, but you will still accelerate very fast through the gears since they are so close together. A 3.1 is the choice r&p for strength and longevity. Significantly Thicker and more teeth than say a 3.2 or 3.4. Cryo treat this box and put it through a remming process to ease the break in and it should hold anything we can throw at it.

Want to go further? The 968 01E is the exact same box as the Audi 01E. If you look at the part number on the 968 gearbox, it's an Audi part number. Here's the cool part for all you custom gearhead thinkers. The European Audi 01E is part of an ALL WHEEL DRIVE SYSTEM!! If any of you can think of a way to fit the front transaxle without much alterations, we could have a monster since it's a bolt in tranny in the rear. I already have 16lbs lightened off my engine to make up the difference of the extra weight of the front transaxle. CEP's dry sump oil pan is a few more lbs. of less weight and give much more room. I'd love to see this happen.

When my six speed is done, I have full confidence on it being more than capable of handling anything I can put it through. For now, I'm having my five speed rebuilt with a N/A fifth gear I'm going to swap with someone who wants my fifth. The six speed is gonna cost and take a few months to get the gears and I just want to get my car back on the road.

333pg333

Bingo Travis. I hoped you'd step in here with that. I couldn't remember what thread it was on and where to look. So in a full on race car you could do this and create a custom fuel cell to work around the changes. I imagine that having the rear suspension is a major upgrade too from our 25 year old design.
Mucho dollero I'm guessing...

Joe, that's pretty much what I'm hearing too. The 931 also has me interested but parts and other issues may not make this a practical solution. As for all wheel drive, I'm not sure if many of us want this, but it's a nice idea in some respects. Remember that there are guys with AWD 911tts that disconnect their front diffs. GT2s and GT3s are rear wheel drive only. Still there would be lots of advantages also. Probably very difficult to impossible to do without maybe tube frame I'd be guessing?

Olli Snellman

All European 01E Audi transmissions are not part of 4WD systems. Quite many of them are pure FWD's cars either with diesel or bensin/gas/petrol engines.
As i mentioned earlier Audi 01E transmissions have been installed into 951's with some 968 parts. With Audi version you can have even working speedometer because it has a similar speedo pick up like original 951's 016 transmissions have.

333pg333

Olli do you see this conversion as a viable improvement?

MPD47

Oh god ST! I'm sorry, let me bow down before you. If you're flat shifting, using any form of anti-lag, preset rev limiters based on a clutch switch, etc you are putting more stress on the gearbox. Period. Call it what you want but it's blatantly obvious what is going on. As well put in another thread about transaxles, 1st and 2nd gear are really only to get you rolling in this car. Maybe it'll take you a few transaxles to figure it out. I have a spare Turbo trans which is used purely for drag passes that I swap in when I wanna drive like an idiot from a dig or do burnouts (see: disposable). Otherwise I use my 968 6spd. As for the Turbo S trans, what DFASTEST said was absolutely correct. However it will NOT hold up to aggressive launches for long. I had a fully built box, Turbo S, quaife, cryo this, shot peened that. Yeah, how long did it take me to blow that apart? 1 season of aggressive launches and other various "abuse" at 400whp. Great. I've blown apart 2 other's that were not built as well. Joe pretty much has the best advice in this thread about having a STRONG healthy transaxle, but other than that, dont go from a dig or WOT in 1st gear and you'll have half the battle out of the way. But judging by your posts Rogue, you wont pay any attention to this advice anyway.

-M

Chris White

As far as the 931 box – parts are much easier to get – it shares a lot of parts with 911 boxes – you can get many, many different gear ratios and lots of good aftermarket parts made for 911 race boxes.

PS - new car in the sig!! This thing is fun, especailly at 30mpg!