Back in July 2017 I installed a new engine. When mating up the C6 transmission to the engine block, I ommitted reinstallation of the engine backplate to make things easier. That turned out to be a terrible decision. Without the engine backplate installed, the starter drive gear will extend 1/8" further backward than designed as it meshes with the teeth on the flex plate. Within 8 months, my brand new Summit Denso-style starter started to grind during startup. The grinding quickly (within a week) deteriorated into a free wheeling starter that wouldn't turn the engine.
The obvious solution was to replace both the flex plate and the starter, and this time, reinstall the engine backplate. So, I did that.
The problem went away for almost a year, but it's back. I heard a little grind upon startup yesterday. This morning the grinding was a little worse. I know where this is going.
I have a new starter on order with Summit. I know I'll be taking a chance by installing a new starter without also addressing the flex plate, which could be damaged. I may end up ruining another starter drive gear (which can easily be replaced, but it's not cheap). My biggest concern is having to repeat the flex plate replacement. What a PIA!
I really thought the root cause of the problem was the lack of an engine backplate, but after this second failure, I have my doubts.
Anyway, I just wanted to post this here to document a relatively unusual issue I've been having with my starter. Has anyone else heard of 429/460 owners who have been running into similar problems?