I recently purchased an HPI Hellfire SS.Everything looked to be in good shape but was far from good shape when I tore it down!I have had one problem tht I cant seem to figure out.I first started the truck up and began to drive it around.But it was only driving the front of the truck FWD.So I went to the shop and tightened the rear drive line to the rear diff.Took the truck back out and I had 4wd for about 2 min.After 2 min the truck stopped moving forward with the engine running, clutch spinning, and the center diff spinning! (when throttle applied)What could the problem be?? Anything would help! Thanks