there is no slipper on the rocketracer..if you mean the differential then there should be no slip whatsoever..if you let the diff slip you will damage the diff plates and diff balls and run a risk of overheating the diff plates and melting the spur gear..you have been warned
if the diff is fully tightend and you still getting slip then you could place a small washer between the small silicon diff ring and the diff, make sure its hole is big enough to go onto the shaft.
this has the effect of putting more pressure on the diff plates.
dave
uk