What does the Gimson45 pull amps wise?
Your not having the best of luck, Ive had one gearbox bust due to a stone, that's it. thought a motor had gone, but it was the connecters, so easy fix.

Over-volting too much...?

AH... I do remember that going in reverse the esc has less amps to play with. so one side is going "forward" the opposite is spinning in "reverse" to get the bot going straight. might explain one side blew and not the other!! When I let go of the transmitter stick, one side slows faster than the other and does a little spin. Looks cool, but annoying! I put it down it this, it has more resistance or something!!!! Perhaps someone with more electrical knowledge can explain!?