I'm rehabbing a Troy-Bilt 360 with a B&S 875EX engine. I have more time than money invested in mostly repairing the stupid push handle that propels the mower. Now after getting it running nice, I find that the the rear wheels randomly lock up when pulling the mower backwards after engaging the self propel. I've pulled the wheels and everything spins freely and the gears are all intact. What would be my next step? Thanks in advance.