Originally Posted by jonrg
You're almost certainly running your rear diff to tight. Can't excatly rember what the manual recommends but slacken it off from book about a 1/10th of a turn more. Or looking at it as a clockface about 5 minutes. That should really help.
The NTC3 uses a ball diff??
I thought it was a gear diff. Otherwise, make sure that the rear wheel turn freely when twisting them in opposing ways. if its hard to rotate them, that makes it slippery as anything. Make it softer using 10K weight or so.