V8 tranny thoughts Options

[Brett W]

Why no just take a standard 915-930 tranny and flip it up side down? This should take the hassels out of flipping the ring gear, you would have to come up with pump and a shift linkage though?

[dan10101]

Felix,
Thanks for the links. After reading that I really want to explore the Audi 5000 Transaxle.

The 1984-1987 Audi 5000S and 1985-1988 5000CS Turbo came with a Getrag front-wheel-drive transaxle that mounts the engine longitudinally. It is relatively light-weight at just 111 pounds.

This transaxle is almost exactly the same as the one used in the 1985-1990 Porsche 944. The 944 input shaft is longer, though, so the Kennedy Engineering Products adapter won't work with the 944 transaxle. In the 944, the front-mounted engine is connected to the rear-mounted transaxle by a drive shaft. By distributing the weight, the 944 has great balance. The new Corvettes are laid out in the same manner.

The only difference between the Audi 5000S and the 5000 CS Turbo transaxles is the gear ratios. The 5000 CS Turbo has wider gear ratio spacing that makes it better matched to a V8 for this conversion, but either transaxle will work. Either transaxle is readily available for about $250 used. Since it is front-wheel-drive with the engine ahead of the transaxle, it does not require flipping of the ring gear and pinion that the Porsche 911 model 915 transaxle does. The Kennedy Engineering Products V8 engine adapter, custom flywheel, 470 ft/lb pressure plate, clutch and starter costs $1092 (January 31, 2003).

The Audi 5000 front frame is simply too flimsy to be successfully adapted to the Montage frame in the manner described for a Toronado/Eldorado on this website. The McPherson strut front suspension would also be dificult to adapt to the rear of the Montage.

It has been calculated that with a few modifications, this tranaxle can handle 400-500 horsepower. Some Porsche 944 performance transaxle parts may be interchangable. The 944 does have a reputation for a weak ring and pinion, so stouter racing parts with a taller ratio would be a good match for the V8 conversion.

The shift mechanism is on the top and side of the transaxle making for an easy adaptation to a mid-engine arrangement. Also the clutch release mechanism is hydraulic so no specially designed mechanical link is required. A custom suspension will still have to be built, but at least the project can be designed around a light-weight transaxle with great torque capacity and extremely low initial cost. These advantages make this an excellent choice for this project.

The same transaxle is used in the 1984-1987 Audi 5000S Quatro and the 1985-1988 Audi 5000CS Turbo Quatro but with a rear output shaft. This makes the rear of the transaxle slightly longer, but it should adapt just the same. Nothing will be attached to the rear output shaft, though, and it will turn, but all the power and torque will go to the half-shafts. The CS Turbo Quatro transaxle retains the wider gear ratios of the CS Turbo transaxle.

It's basically the same transaxle as my 944 and 951. I'll buy the fact that the NA transaxle may be weak, but I can attest that the 951 trans will take the abuse. So changing some internal parts may be in order to really be able to flog it, but even without that, it should handle more torque than the 901 with better gear ratios.

I need to do some more research on gear ratios, but with those trans available at pick-n-pull for less than $150 out the door, I can see it worth looking at.

Ok, so shoot me down, who has tried it and found it to be junk?

Where are the weak spots? How can we fix the problem areas?