68 D100 4 speed 318

This is the huge 3 bolt deal

My old napa starter started getting tight after the engine heated up. I replaced with another napa and it grinded every time i tried to start. That happened for a day or so and i loosened it and was able to rotate it slightly. I thought i cured it until a single time last weekend when it happened again.

Any ideas? Anyone ever put a dab of lithium grease on the teeth to help it mesh? <img src="/ubbthreads/images/graemlins/shruggy.gif" alt="" />