[potreinas]

please, try other tests:
take out the motor from the car and make some throttle brake, reverse etc...
This way you can see if the problem is the tipical bracking issue of the mgm that doesn't do allways.

If your tests with the motor out the car run smoth all the time without reversing, or instant braking.. then try with tne motor on the car and shim diffs perfectly.

let us know about the tests.