What other AWD systems use a Torsen center differential. The only other one I know of is the Jeep Grand Cherokee's Quadra Trak. Why do almost all AWD systems in cars tend to use a viscous-coupling diff instead of a torsen? Audi does not have a patent on the Torsen since it's made by a different company. Are there disadvantages to this system versus a viscous setup? A torsen always transfers 50/50 unless there's slippling, whereas most viscous system transfer power 95/5 until there's slipping. Are viscous setups lighter and cheaper? The only common like I can see is that all the cars w/ AWD viscous systems have transversely mounted engines. Both the Jeep and Audi use longitudinal engines. Anyone have some insights/answers? Just curious.

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This is a very good link! <p>Kevin C.<br>Silver 1.8TQM<ul><li><a href="http://www.eskimo.com/~eliot/awd.html">Introduction to AWD</a></li></ul>

It's essentially a clutch, similar to a Haldex system.<p>The FAQ mentioned in one of the followups (and in the FAQ section) has a really good explanation of AWD and which makes/models use which system. IIRC only Hummer's and Land Rover's use Torsen (in addition to Audi)

My automatic Outback (which I traded for the Audi) was split 95/5, but that's only in the autos. My Subaru Impreza 2.5RS manual splits 50/50, which I much prefer.

There are different ways of using a viscous-coupling.. <p>You can use it "stand-alone", then you get this 95/5 split.. (Volvo AWD, VW Synchro and many others.. This sux..)<p>..and you can use it with a normal diff (like the Subaru Impreza, Escort Cosworth..), and split as you like (33/66 for the Ford Escort Cosworth). This is more fun.. <p>Ofcourse the visco is used more often since it is much cheaper.. Drawbacks is that when it locks, it splits 50/50 (or almost 50/50, since it is a limited slip coupling). The Torsen can split from 20/80 to 80/20..

...the uNaBiMmEr'S girlfriend on New Year's Eve. Wow - UNlimited slip differential!

NT