B7 S4 4WD System?

[R33]

Does anyone know how the 4WD system works on the S4?

I pulled away hard on a wet road this morning in a pretty much straight line and got loads of wheel spin from the rear wheel while the fronts stayed planted. I've not had this happen before and I was curious what the split was in the 4WD system?

I assume the system isn't one that changes it's torque split between front and rear depending in grip, and that it's just fixed? Could anyone give me an explanation of how it and the diffs do their thing?

[BlingBling]

I believe that B7's have a 40:60 split where as the B6's was 50:50.

[xyber]

I've got a B6 and I've lit the rears up once. The fronts missed a big man hole cover, the rears didn't and off they went. It was a complete fluke and I've never even come close since

[gottanS]

To add a bit of confusion, the B6 has a 50:50 drive split on the centre diff, the early B7's are the same as the B6 but some of the later B7's have the 60:40 split (2007 onwards).

When you says the rear wheels span, was it both or just one? I believe the front and rear diffs are standard diffs that will spin the wheel with less grip and the traction control should brake the spinning wheel to maintain traction. I know in my B7 pulling away with the passenger wheels on wet grass with the drivers side on wet tarmac was dead straight with no fuss so either traction control is working or a I have one or two limited slip diffs in there somewhere.

My first Audi was an A4 quattro and this did have an limited slip diff in the back, defintely noticed its loss when Audi changed the rear diff under warranty. The car would spin the side with less grip when doing same as above.

[R33]

Thanks for the replies. I had a little typo in my original mail, I meant to say both the rear wheels were spinning. The traction control went nuts but it just meant I didn't get away as quickly as I needed to.

Overall I was just interested in how the diffs and 4WD system worked.