I have a 99 f250 superduty with a 5.4 triton in it. Automatic. It shift properly when cold, through all gears, once warm, it won't shift into third and overdrive. If you get onto the highway when it's cold and get up into overdrive, it will stay there once warmed up. But if you slow down and it shifts down, it won't shift back up. Once parked and cold, it will work properly once again until it warms up. Any ideas whats causing it?

 

My guess is that the seals in the direct clutch are worn and don't always seal.

 

I had a similar issue in a chev tranny. It was a valve that was sticking in the valve body. Do you think that could be a possibility?

 

these trucks are know to have leaking feed bolts. they loosen up and cause por shifts, weak, shifts, or no shifts or forward gear movement. You simply remove the valve bodies and put new red high temp thread lock on one bolt at a time and torque to 14ftlbs. heres a pic of the trans that shows the feed bolts

 

my dads 2000 F350 7.3 did this as well as my buddies 2002 5.4 f250. All it took was a half hour and 8 quarts of new fluid

 

Fluid is brand new. I got it working though. The entire truck was full of snow and ice. Let it sit in a heated building for a while and now it works fine.

 

what does snow have to do with it not shifting seems odd? Ive had my truck in four foot drifts, snow going over the hood playing around. you couldnt see the axle or the frame for a week after and it never acted up at all...

 

The conections were iced up and not working properly. Unplugged the conections and let them sit like that for a while. Worked great after.

 

ah that could do it, did you put dielectric grease on the plug before you hooked it back up