Help...truggy doesn't go...

[What's_nitro?]

Are you using thread lock on all of the set screws throughout the drive line? Motor pinion?

If all 3 diffs have been properly rebuilt, and all the CVDs are in good order, there should be no problem. I think you need to tear it down again. Even with no fluid in any of the diffs you would have plenty of power to the rear wheels if everything was mechanically correct.