I've recently had the rear diff replaced on my 05 STi type UK as the original was starting to whine really badly.

Dont know if its my imagination, but in the bad weather we've been having the car doesnt seem to feel the same, when pulling out of junctions etc the back end doesnt seem to slide as much as it used, seems as if though one of the back wheels is spinning rather than both.

What sort rear diff would have been fitted originally? and is there a way to find out what is now fitted?

Thanks

Jack up the motor, all four wheels. Turn one rear wheel, the other rear wheel should turn the same way if it has a limited slip diif, if it turns the opposite way it is a regular diff.