My ''75 F250 with 360 and C6 slowly took longer to get moving once started. It finally refused to move at all in any gear. Trans shop told me it needed the C6 replaced with a rebuilt unit. Instead a buddy and I tore it down and rebuilt it. Once we got into the trans it looked pretty good, seals were not hard, etc. Installed a rebuild kit and new torque converted anyway and put it back together. Test drive went well the night we got it running. Next day we took it for a longer (5 mile) drive to a gas station and it worked great. When we went to leave it would not move. Pushed it out of the way and puzzled over what was wrong. After 15 or 20 minutes tried it again and it worked, drove home without trouble. Pulled in to the shop, shut it off and started it again. Would not move. Next day tried again, after it ran a couple of minutes it would move. Shut if down and let it sit a few minutes and checked the fluid level, it was up a couple of inches on the dipstick. Got it running and after several minutes checked the level again and it was where it should be. We think the torque converter is draining down.Any thoughts or suggestions?

As a note, prior to my owning it someone had put a shift kit in it as they used it to pull a large trailer. Shifts would snap your neck, and we think the trans was rebuilt at that time given the condition of the seals. Had ordered a new shift kit to try to get back to something a bit milder, however it had not arrived in time so is a project for another day.

 

I would put a gage on it and see whats going on first.

 

Thanks "mark a", I did and there was no pressure. Out came the trans again (REALLY regretted having put the cross-member back in under it). Found the pump had failed. I had it apart initially and put new seals in it, and it looked good. However when i took it apart again there was a lot of dark gray sludge in it. Bought a rebuilt pump, installed it and put the trans back in, after draining the converter, flushing it out, and using new fluid. Worked great!

This time I left the cross-member out until I knew the trans was good. I have seen several posts on this cross-member, however while it was not easy it was not that difficult to work with. The 4 lower bolts were easy. The 4 upper ones (through the top frame rail) were more difficult. The first time I pulled it I did it myself and it was a challenge. The second time I had help, with me underneath and a deep 3/8" drive 9/19" socket and breaker bar on the nut from the bottom. My friend, and in some cases myself, was able to work the bolts using, at times, a box end wrench, ratcheting box end wrench, or a socket. Once all the bolts were out, the cross-member must slide towards the back, and over the mount for the cross-member under the tail shaft. This means the trans must be supported, I used a trans jack from the front so once the load was off both cross-members could be removed. Putting it back in was basically the reverse process.

 

The cooler and it's lines are one place that crap hides. Another place to pay particular attention to is the rear shaft in the trans. Often it gets overlooked and it holds more fluid than one would think.