checking a limited slip diff

[Pig Skill]

Guys

Will be having a day messing with my E46 M3 today and getting it on the ramp. Amongst checks I want to check to Diff. Anyone know how it can be checked to see if it is working?

As my understanding goes - If I rotate one rear wheel the other should rotate in unison. If someone hold the other wheel I should be able to turn the other but with more force needed. Is it as simple as that?

If it was goosed what would be the tell tale signs?

Many thanks

[dtmpower]

Even an open differential will rotate the wheels together on a ramp due to the amount of friction involved.

The best way to test an LSD is driving from stationary on full lock and pulling away hard in first and seeing if the back end of the car kicks out.

Alternatively a drag start and checking for parallel black tyre marks.

[bramley]

I've had a few of my cars on a ramp and those with an open diff have always spun the other wheel the other wheel, and those with lsd have always spun the other wheel the same way, so that test has been accurate on my cars.

I agree though, that there are far more fun ways of testing a diff!

[Gene Vincent]

Put one wheel on a very slippery/wet verge and the other on tarmac, if you move off readily your diff. is sound if you don't move and you spin or it graunches and moans and clicks like a cricket you either don't have an LSD or it is fookered.