I've recently upgraded my differentials with the traxxas brand spools and tonight I tried install traxxas brand steel driveshafts after the stock ones broke but the cup that goes over the spool ends does not fit. I tried sliding the new driveshafts over the old differential output shafts and they go right on. Obviously the problem is with the spools but doesn't make since. Has anyone else ran into this problem? Any easy fix? I would understand it they were aftermarket parts but they are alboth traxxas brand parts