Hello,
I have a 92 F150 with 124,000 miles. 6 cyl (300-straight) Not sure what transmission is in it. I bought the truck in 96 with only 14,000 miles on it. It did this when I first got it but only very, very, very occasionally. Now I have the problem all the time espacially after it gets hot. When driving it will shift from one gear to another so hard that it actually jerks my head. It feels like the tranny is going to fall to the ground when it does this. If I stop and shift it down to 1st and then back to drive it will stop doing it for a while as if the shifting into first "resets" something. Also... when I stop and shift it into first to "reset" it will grab and the truck will crouch or lunge...for lack of better description. Someone told me it sounded electrical... like a shifting solenoid or something. Does it have a shifting solenoid and where can I find it? Any other suggestions?

 

Do you know what transmission it is? Take it to the transmission shop and have them scan your ECU. There is most likely something slipping or another problem which is causing your ECU to go into "Safe mode" which applies 100% line pressure to the transmission.