FINALLY, I think it's fixed....

[othello]

I feel for you orangecrush ... this behavior is annoying and could become costly because of the extra stress put on the drivetrain.

Today we drove this mugen Mbx5t i mentioned above (MGM 16018, Neu 1515/1y) and this time we noticed a clear mecanical noise (for a split second) when we went from top speed to neutral. After checking the diff we saw that the pinion gear was completely worn out (back diff) and the front one didn't look much better either. After replacing those parts i will post our findings.

The test proteinas suggested seems the best way to rule the diffs out of the equation.