What would cause uneven tread wear in the rear???

95Vert,

The rear does not get aligned on our cars.

The more likely cause for a rear tire wearing unevenly is a bent wheel. Get an alignment shop to do a runout test on the wheel in question. That will tell you if it's bent.
 
I noticed that after doing some counter clockwise donuts, the outside of my right rear tire seems a little more worn than the inside. I think that the momentum from the car made it eat more tread off of the outer part of the tire. Donuts eat up a ton of tread life after about 3 turns because of how hot the tires get, I have actually gotten hit in the arm by a piece of rubber off of my tire (stuck in my arm hair).