From the initial install there were not any issues that I noticed with the transmission. It shifted through the gears fine. Driving around town or on the freeway it worked fine.
When I noticed the thrust wearing out was when driving uphill slowly or slowly in reverse there was a grinding sound coming from the bellhousing. When I went to look at what was causing this, I noticed the crankshaft sliding forwards and backwards in the block. So the flex plate was riding forward and hitting the engine plate between the bell housing and block.
Then I tore the engine down for another rebuild because there was metal shavings in the oil and valve train.
The only other issue I had was the front hub of the torque converter was firmly stuck into the back of the crankshaft. It took 2 - 3 foot pry bars to get it separated.
It was there that I began checking the flexplate and torque converter. I called around to a couple manufacturers and told them what I was doing and we determined I had the right combination of both the flexplate and the torque converter for my application.
I have now installed the newly rebuilt engine and so far have not had any problems with the transmission. It is operating very similar to 8 months ago. Shifts fine and firm, downshifts, good operating temperature, etc. Nothing saying anything is really wrong.
I just can't help but think something had to push the torque converter into the crankshaft causing the thrust to wear out.
The only next steps I can think of are pressure checks on the transmission and then making sure the Torque converter pressure switch is working correctly. I am sure there are other areas to look at but transmissions are not my expertise.