Old Dog

Thirty years after making its debut, Audi permanent AWD system is entering a new generation. With an intellegent combination of mechanical and electronic components, the quattro drive system once again sets the benchmark for agility and driving enjoyment.

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Source: Audi Magazine #4/2010

Jusforfun

I see two small problems.
1. as seen in the ever popular online videos if you stop the car completely and then give it lashings of power none of the drive is sent to the gripping wheels at all. Hence all the silly videos in which you will observe the driver always carefully stops first then applies too much power when in fact any movement would have resulted in 85% going to the axle not on the rollers/ice.
Its almost the greatest anti Audi spin going except I got stuck in exactly that situation. Solution roll in any direction until you can start to apply drive again. In actual driving or moving conditions it never arises. That said this diff does not address and does not overcome the static slip problem.
2. As far as I am aware that Torsen centre diff (the 5:1 version) is not in either Q5 or Q7 as yet! It is a lighter version being fitted to the A4.

Coolieman1220

Pretty sure the Q7 uses a borgwarner varient for center diff....

CrustyNoodle

It would be nice to know for sure which series Torsen the Q5 uses.

gat821

The Q5 uses the T3 torsen. Compared to the T2's equal torque distribution, it provides the 40:60 front:rear split.

This crown gear diff in the OP isn't a torsen. However, it does look like the clutch actuation is mechanical, triggered by speed differences in each shaft, rather than electronic and relying on sensors. Hopefully, this makes torque transfer as quick as the torsen.

It can also fully lock the diff, and will send torque to the other shaft even if one is on rollers/ice, so jusforfun, it does solve the torsen's static slip issue.

CrustyNoodle

Based on the 60:40 split I'd assumed it was the T3 but I'm yet to see anything official that would confirm it. I suppose Audi are unlikely to come out with any literature saying "T3" diff.

gat821

Here's some animation of that crown gear differential.

http://www.youtube.com/watch?v=xZ9x9jHkTrg

It looks like the rotation of the smaller gears when wheel slip is detected is what moves the clutch plates to divert torque front or back.