Special Ball Differentials.........help!

[bobstains]

I've built my TB evo up, installed the motor etc but when you start the car forwards it spin's the front wheel's but the rear don't(but they do when you get the car moving). likewish if you reverse the car, the motor spin's but reverse is quite slow..............it this correct or have I got a problem.

do the 'Special Ball Differentials' work by powering the front wheels to start off and what seems like a 'clutch' to sort the power out to the rear?

[cobra81li200]

seems like you've got a problem. Make sure your diffs are tighten enough (when you lock one wheel and the spur gear, it should be very hard to make the other wheel turn). Check anything else that could be wrong aswell.