The drill was smoking while in use at the rear of the drill

Hi, these units tend to heat up over extended use. It is possible that your brushes have worn down and need to be replaced. The contact area around the commutator, (where the brushes push against), should be cleaned gently with ultra fine steel wool. Also, the gaps between the contact points of the commutator should be free of any conductive dust left behind by your dying brushes. Since the drill needs to be disassembled in order to do this, check any connections for weakness and any more conductive dust that may be shorting something. good luck.