Transmission not shifting?

It was the EPC wire going to the transmission that was corroded.

Transmission problem
1989 Ford F250 Four Wheel Drive Manual 80000 miles

I have got a 1989 Ford F-250 7.3 Liter Diesal Straigh Drive and it has been setting for 6 months and has not been cranked I went out there today and cranked it up, it run fine, but I left it running and pushed the clutch in and tried to change gears but they would not change. I went to the auto parts and got a new slave cylinder and put it on and bleed the line but it still did not change gears.

My transmission will not shift from second gear to third gear. It goes beautifully from first to second and then it just stays in second.
If I drive long enough, about 15 minutes, the vehicle, still in second gear, will begin not to catch, then not catch at all. Step on the gas and you get nothing, but the engine is revving up while the transmission slips completely, while still in second gear. If I roll to a stop stopping the vehicle, then step on the gas, the transmission will then catch again immediately. I can go through first, then second and will not shift any further, and soon it will again disengage.
The cycle will repeat itself, with the engine eventually begins to overheat.
The catalytic converter was installed where it actually touches the side of the transmission valve body area. Could that cause the transmission to overheat? Also there were a lot of metal shavings in the pan when I removed it. I did change the fluid and added a lubricant, it did not work.
I have the valve body off and I am preparing to take off the plate to clean it and check the valves.

If the catalytic converter is touching the transmission and it heats the fluid, that is a possible explanation of why, as I drive, the fluid heats up to where it is causing total slippage?

But, if I stop for a second and then take off again, first and second work fine, but it still will not shift to third, and the time between stops becomes shorter, the engine gets hotter, until I am revving the engine with minimal result and third still will not commit. I do not push it any further.

How serious is the cat touching the transmission scenario? I assume I should fix that.

I was told the metal shavings could be the cause of the valve sticking?

I have the valve body out and was going to remove, clean and replace?

My Ford-F250 had this same problem. I would get the catalytic converter fixed right away. That ended up being the source of my issues. As soon as I got it moved and changed some sensors, it shifted beautifully. I hope your solution is as simple.

My 98 Chevy Tahoe is doing exact same thing. I had the transmission rebuilt it worked fine for a yr and now it's acting up again. It will shift up to 2nd and that's it.
Did you get it fixed?

My '76 F250 460 is having some issues. The automatic C6 Transmission will not shift into any gears. I have already done several linkage adjustments. She has broken down for about a year. I finally got her running after replacing the fuel pump last night. The last time she was running she wouldn't shift into reverse. So now she starts, but is only stuck in what I assume to be the parked position. Any ideas of what the fix might be? I'm aware that the c6 tranny is pretty simple to work on and has many common issues, but I have yet to find a link on this particular issue.

The tranny fluid is clean and full. I have not yet attempted to put it in neutral and push it. The linkage moves in all positions as well as the shifter. I'm not sure if the whole tranny needs to be rebuilt or not. I've also read that it might be a vacuum line causing the issue.

Just wondering the best option to fix transmission in my F250. It has a ZF 5 speed manual box. Dropped the oil out of it had metal through the oil, one of the shafts are buggared and also a bearing or to are stuffed. Have'nt got all the info yet but was wondering wheather to rebuild it or just source a replacement transmission assembly