Has anyone here done this before? I'll soon be replacing the rear subframe on my car so I figured what better time to swap the diff than now.

My style of driving is simply just not compatible with EDL, and my mechanic told me he thought I'd be a lot happier with the torsen rear diff that comes standard on all Audi V8's. Only problem is we never got into details about the procedure of this swap. He's currently on vacation and I don't want to bother him, so I was hoping someone here could help me out. Is it as simple as just removing the old diff (housing and flanges included) and swapping in the new one? Or am I going to need to do some internal disassembly?

 

Holy shitsky Austin, it's been so long since I've seen you post, I thought you died, or worse, bought a BMW or something

The only way I can think of to make it work unless for some remote reason the driveshaft and axles will bolt up, would be to:

Use the front half of your driveshaft and find a way to mate the rear half of one from the V8 donor. Mate them at the center support bearing.

Try to put inner CV joints from the V8 onto your rear axles or your outer CVs on the V8 axles, so the proper parts will be in place to connect at the diff and hubs.

You may likely have to have custom halfshafts and a driveshaft made to do the swap though. There are shops who do that. Have you given consideration to the gearing in the V8 diff though? With a very different torque curve than your engine, that gearing may be all wrong for your car.

 

maybe this helps?

V8 rear diff into 01E case information... :: motorgeek.com

 

Neat build for the center diff, but I'm only working on the rear diff for now.

Haha, no new cars since the last time you heard from me, just a couple beat-up trucks that will never take the place of my Audi. I needed to spend a lot of time saving enough money to get my Audi back on the road, which I'm finally ready to do.

I figured if anything was to be modified, it would be the differential from the V8. Didn't realize I'd have to cut axles and driveshafts for this to work. Assuming the gearing is different, there would be no affordable/practical way to make this work? I don't want this custom oem build to cost more than an aftermarket unit would.

 

Hey now, be nice, be nice! i was a previous BMW owner for years and have had 5 of em, love them to death. but very boring interior and wanted something new (audi) but hey all to his/her own

 

Yeah, beamers are nice cars, best handling RWD IMO, but I can see where Jeremy is coming from, they are filthy rivals and will get no love on an Audi forum.

 

I read a few things about doing this. I'll have to look back on my other computer to see if I saved the articles. Basically what it came down to was machining the V8 diff to fit the smaller bearings of the stock open diff. You will reuse the housing, pinion, ring and CV shafts.

While having a torsen diff rather than open has a few advantages, it will not behave as a true limited slip differential. As soon as you lift a wheel, it will behave as an open diff once again. All it can do is to change the torque bias to the left and right wheels much like the center diff in our cars.

 

That's cool that the V8 diff casing can be modded to accept the B5 shafts - I was not sure if it could be, which is why I only mentioned what I did. Hopefully you're back on the road soon and can come back down for another meet - trust me, they've grown a lot and the fun factor has increased to an epic level.

And I have no hate for BMWs, although I'm a little less accommodating of the (locally at least) ****** that often end up behind the wheel

 

Good info, makes me a little more optimistic about this whole thing. So the gearing won't be an issue? Lifting a wheel does concern me though, as I do intend to AutoX this car at some point. This mod won't make this any more of a problem than it already is though, right?

Can't wait to get back down there to the meets. Sorry if you all thought I was gone for good.

 

No, it can't make the problem worse, but I couldn't see it making things better enough to justify the cost/time. With the center Torsen differential if you break a CV shaft or lift a wheel all of the power will go to that wheel and the car will not move. Adding a second Torsen at the rear doesn't really solve this problem.

I do autocross as well, though not yet with my A4, but I would spend more time/money on suspension to keep yourself from lifting a wheel rather than on a differential that will change the torque bias between the left and right rear wheels.