So my buddy jorvis79 has a c6 in his 79 F250 4x4, he has only ever driven the truck on/off the trailer before he started restoring it. We dropped the pan to change the fluid and found a broken plastic thrust washer so we pulled it for a rebuild. (To preface I am a ford tech when we are not in the firehouse) I have rebuild tons of newer trans (6f35,6f55,5r55s,cd4e’s) but I am currently stumped. I put in all new frictions/steels ect checked end play right in the middle of spec. Trans spins either direction when I spin input shaft. I install the torque converter and it will spin fine clockwise but locks up to the left(counterclockwise) for every other trans I’ve ever done the torque converter once seated spun either way. I thought possibly this was a c6 thing until I tried to spin the tail shaft and it won’t spin in reverse. I remove the pump put the input shaft back on spin the converter on the shaft forwards/backwards fine. I took the pump apart no broken gears turns fine. I am thinking the torque converter is somehow internally broken? It’s acting like the entire converter is one giant one way clutch. Not sure if anyone has seen this or has advice? I wanna say it’s the tc I’m not sure what else it could be, thanks for anything

 

If you can't turn the output shaft in both directions;;
it sounds like the intermediate band adjustment is too tight

 

It spun only in one direction, it was the torque converter, new one and it spun both ways like butter