Re: Question: 80Q "limited slip" center diff doesn't limit slip...

[quk@isham-research.demon.co.uk (Phil Payne)]

> He went into a 2 level parking lot with a steep ramp, and drove up on =
> the edge of the ramp so that the right rear wheel came off the ground, =
> but all others were firmly planted. The wheel in the air spun free as =
> the care came to a stop and started rolling *backwards* until the fourth =
> wheel hit the gound again (and then made a lot of noise and smoke 8-)

> This doesn't match my understanding of "limited slip" which is this: It =
> allows only a certain percantage difference in rotational speed between =
> it's two sides. Namely, for the rear shaft to spin at 100 rpms, the =
> front "shaft" must be spinning at some percentage of that, e.g. 60 rpms. =
> Well, if the rear axle is spinning forwards and the car's not moving, =
> that's pretty much full slip, right? And if the car can go backwards, =
> then it's really full slip, right?

The Torsen senses _torque_, not rotation.  It was probably applying more
toque to the front axle than the rear, but you were artificially not
applying enough to overcome gravity and so didn't see the fact.  The
Torsen Audi used in these cars doesn't go as far as a 0-100 split, so
there's always about a fifth going even to the slipping axle.  The
rear differential is (relatively) normal, so it spins the free wheel.

--
 Phil Payne
 UK Audi quattro Owners Club
 Phone: 0385 302803   Fax: 0870 0883933