Sure thing. Clutch-type LSD's have clutch packs that limit the speed difference between the wheels. Most factory BMW LSD's come with a 25% locking ratio. This means that for whatever amount of torque is applied to the wheel spinning more quickly, at least 25% of that amount will be sent to the other wheel (generally the one with more traction). Anything more than about 40%, and you will be able to feel the diff catching when going around a tight corner. The fixed slip difference means that the car will consistently catch in the same place every time. A viscous diff, on the other hand, is a type of torque-sensing limited slip. Basically, the diff is filled with heat-sensitive fluid. As the wheels spin at different speeds, the fluid is heated up, becoming thicker. This is called an increase in viscosity (hence the name). The hotter the fluid, the thicker it gets, and the more of a locking facter you will have. The problem is, in an autocross, if you enter a corner on the gas, the diff will act like an open diff (spinning one wheel) for a short time until the fluid heats up. Eventually, it will heat enough to stop the pinning of that wheel. Because fricion and heat are no longer being generated, the fluid will cool and become thinner. The inside wheel will begin to spin again, and the cycle will start over.
Hope this helps. it is kind of hard to explain over the internet
EDIT: just found this, and it happens to be BMW specific. Good idea of how clutch-type diffs work:
http://members.aol.com/agspeed/LSD-lock.htm
Topic: diff question (Read 3120 times)