Rear mounted transaxle and clutch/driveshaft inertia

[Gabriel]

Hello, I'm new here on the forum. I'm building a drift car in which I plan to use a VW 016 or 01E transaxle mounted at the rear of the vehicle, paired to a front mounted engine.

According to my plan, I was going to have the clutch at the engine. However, some people pointed out to me that the inertia of the driveshaft spinning would act as a flywheel for the transmission, interfereing with the proper functioning of the synchros and would make it difficult to shift quickly.

I know these transaxles were used in a rear mounted setup in older Porsche's, does anyone know how the clutch was set up in those cars?

I'd like to hear some third party opinions before I put together something that doesn't work.

Also, I do not want to use a torque tube like in the Porsches. Does anyone know if the bellhousing cover from any of the Porsche models has a bearing supporting the driveshaft, or does that bearing reside in the actual torque tube? Will that bellhousing cover bolt to the 01E?


Thanks in advance

 

[Bob Putnam]

There's a reason that the Porsche uses a torque tube: it allows a small diameter driveshaft without the need for universal joints. The polar moment of inertial of the system is minimized. With two universal joints and a tubular driveshaft, you're probably doubling the Moment of the disc alone, which means your synchros are going to take a beating.
Polar Moment Calculations

 

[Bob Putnam]

*On the other hand, if you treat the gearbox like it had no synchros at all (and accurately double-clutch up and down), it will last forever...

 

[Dylan]

The Porsche setups use a standard-position flywheel, clutch, pressure plate, and then use a solid-mounted torque tube with a balanced 1.5" diameter shaft running from the bellhousing back to the transaxle, with a female coupler to connect the male torque tube shaft with the transaxle input shaft. This torque tube shaft rides on two bearings at either end, which are in the torque tube itself.

Using a torque tube is really your only option, and the benefit is also that your drivetrain is one solid unit from engine to transaxle, so you don't have to worry about the engine/trans shifting/torquing independent of your rear end.

Porsche torque tubes (steel shaft, steel housing) and C5 corvette torque tubes, (steel shaft, aluminum housing) are relatively easy to cut apart and shorten/lengthen, and don't break the bank. Using a driveshaft that would spin at engine RPM is not a good idea. Say you've got a 5000RPM redline....that's what the driveshaft is spinning at, whether you're doing 5k at 25mph or 100. Not what I want to have right next to me through a thin floor. Torque tubes are used for a reason. The torque tube housing walls are massively thick for a reason.

 

[Gabriel]

I had hoped to avoid using a torque tube, but I guess it looks like that is my only option.

The gearbox I want to use is the 01E, but I've read that the 01E from the Porsche 968 is different than the 01E used in other FWD vag cars. Can someone tell me if the bellhousings are the same (or at least similar) and more importantly, are the internals just as strong?

 

[Jimmy P]

Gabriel, Contact Scott Dewitt from WWWW.ADVANCEDAUTOMOTION.COM in Texas. He used to be a Forum Supporter but I've not seen him post in some time. He is an expert in the O1E box and should be able to answer any questions you have. 720-443-2771.

 

[Gabriel]

Thanks for the info, I'll try to contact him.

I've came up with another idea - can someone tell me if any of the available porsche driveshafts have splines that mate up with the standard vw/audi 01E?

If so, I can probably fabricate my own bellhousing "covers" allowing me to use the standard 01E as opposed to the one that was Porsche 968-specific.

 

[Eric A.]

The Porsche drive shafts are a different spline than the regular 01E but they use a coupling between the driveshaft and transmission so you could have one made up with the correct splines on either end. It will need to be longer than the stock Porsche part since the input shaft is shorter on the 01E. The bellhousings will be similar with maybe one or two holes slightly different but I think they could be made to fit.

 

[Scott]

I had hoped to avoid using a torque tube, but I guess it looks like that is my only option.

The gearbox I want to use is the 01E, but I've read that the 01E from the Porsche 968 is different than the 01E used in other FWD vag cars. Can someone tell me if the bellhousings are the same (or at least similar) and more importantly, are the internals just as strong?

The 968 trans have a very different diff housing than the 01E I think only one or two bolts are common to the two. The Porsche 016 has a bell housing bolt pattern that is closer to the 01E. i'm confident that you can make a 944 torque tube work with an Audi 01E but not so sure about a 968 torque tube.

A big benefit the 968 01E has over the other version is the ring gear is much larger and it uses a G50 style diff so you have a great many diff options and a much stronger diff and ring gear.

The input splines are also different from the Audi/Vw 01E to the Porsche 01E.