I don't know about the S90 but I do know about the '92 940 turbo I had on the road. When I first started driving it I had checked to see if it had an LSD rear (solid axle) in the time honored tradition of spinning one wheel and watching the other - the other spun in the opposite direction and I figured it didn't have LSD. It wasn't till the car was "totaled while parked" that I discovered that what it did have was a "lock-up" rear. I went to check if the LR wheel had sustained damaged and jacked up that side with a floor jack from the back--started the motor-put it in gear (automatic) at idle to spin the wheel and the car started to jump forward on the RR. The "lock-up" rear has a ratchet mechanism that transfers power to the wheel with traction rather than a clutch pack like you'd find in a normal LSD. Be careful how you go about checking yours. -- Dave