2001 F350 transmission electrical problem

[B20STROKER]

I have a 2001 F350 with 90000 miles. The transmission is having intermittent issues with locking up. When it's working normally it will run around 2200RPM at 70 mph and when I let off the accelerator the rpm's will drop slowly as the truck slows down. When it acts up it shifts through the gears but will be running 3000RPM at 55 mph and if I let off the accelerator the rpm's will drop back to idle. The way I get it to shift correctly is to pull over and shut the truck off then start it back up and it will shift fine. It will continue to shift fine no matter how far I drive as long as I don't shut the truck off. It is completely intermittent and does not have this problem everytime I drive it. The truck is stock with the exception of an AFE intake and an MBRP 4" turbo back exhaust. Transmission has been serviced at regular intervals. Any info would be greatly appreciated.

[ipz2222]

It's not shifting to 4th. Possible sticking 3-4 shift valve in the front v/body or loose center support bolts.

[fwbkent]

you have a code in the PCM, needs to be checked. The trans is in failsafe most likly is why the converter is not locking. Also the reason you have the problem on the next key cycle is because most codes take 2 drive cycles to set. Thats part of the OBD II .

[ipz2222]

fwbkent, fyi, failsafe will not cause the tc not to lockup on the psd.

[B20STROKER]

It seems to be shifting into 4th. I guess I'll carry it to the shop next week. I was hoping it might be something simple I could take care of myself. Thanks for the information.