What differences (if any) were there in transmission, rear suspension, differential, etc between the SL500 with the V8 and the SL600 with the V12? Did the added horsepower and torque of the V12 cause those vehicles to come equiped with more heavy duty drivetrains? I have not been able to find any information on this anywhere.

 

Which SL year. If you mean the W140 based SL (R129), then for each model year they all had the same transmissions and same rear suspension, differential and the rest of the body was the same too I believe. They were way over built back then!

Not sure about the newer ones though, probably all the same, it would cost too much to have major differences between each model.

To confirm, have a look at axle ratio specs, I think they are all the same...