I just got done cleaning the diff. Since the spur gear is basically also the diff gear it is fairly easy for dirt to get into the diff. It is very easy to disasemble to clean, so I figured I'd clean it considering how dusty the area was that I was driving in.
While looking the car over I realized that I broke a part on my run
!. Apparently tightening that adjustment nut down wasn't the best idea (neither was accidentally spinning backwards and hitting a curb, which is most likely what did it). The small aluminum stud that the rear motor pod/suspension rides on snapped off at the base. It is hollow and is threaded inside and out, so it isn't really designed to take impacts. I guess you could call it a weak point. However, if I hadn't tightened that nut down it may have had enough movement to absorb the shock and may have been ok. Also, if I had the body mounted it probably would have taken the impact and left the car unharmed. Either way it is a $2 part, which is a pretty cheap weak point to find. It is also very easy to replace. I literally had it out in about 30-60 seconds (three hex screws).