Its been a while since I've had a TC3 but I think the setting is tighten the diff down and back it off 1/8th of a turn.
It could also be a bad thrust spring, also if the bushings or the bearings are to thick you wont be able to tighten them enough. And if they are the plastic out drives they are a little funny feeling any way. Also theres a TC3 thread around here some where? I know they can figure it out.
Have you rebuilt it yet?