quote:

look at the round detent around the crank bolt section

The old TCI had a detent (both crank and converter mount) and the new ATI plate does not use one, it’s flat. I assume TCI does this because it’ .028” thinner than the thicker ATI plate. I also removed the paint from the crank mount surface on the TCI plate prior to mounting. The ATI is not painted in the crank mount area. Like I wrote prior, I could not see any metal surface cracking anywhere but no doubt it’s fatigued.

you have done your homework for sure,glad you found it

When you checked the flywheel bolts previously, did you back out and retorque? Do you sand the powder coat off under the bolt head? I’m betting they were loctited and the powder coat wore and you lost clamp load.

I used to have this problem with blower pullies on the crank. Aluminum would fatigue under the bolt head. Bolts were glued in with the strongest stuff I could find and match marked. Bolt would stay put but aluminum would yield, clamp load goes away, bolt becomes a pin and pulley would shear the bolts off.