I have a 1997 F250HD, 5.8, auto trans w/OD 225k miles. Recently while in overdrive (above 50 mph) it intermittently has a light downshift and then right back into normal highway gear. Otherwise The trans shifts perfectly, smooth and quiet, no slipping at all. Could this be an overdrive issue? Thanks

 

Your transmission is 100% computer controlled, check for codes. The same computer for the engine controls the transmission.

Even though your truck is a 1997 F250HD model it could be OBD-I or OBD-II, Do you have a Data link inside the cab near the the middle of the dash (under the ash tray)?

 

It doesn't have the OBD port under the dash. When I bought it I tried to have it checked for any codes. The mechanic told me that the over 8500 gvw models don't come with them in my year model.

 

Most '97 F-250s (and F-350s) were EEC-IV (often called OBD1?), but some (California trucks?) were OBD2. They were all one or the other, and both have the engine and auto trans completely controlled by the computer.


If it's OBD2 there will be a data port under the dash. If it's EEC-IV the data port is under the hood, probably near the left hood hinge.

 

Thanks for the info. I have had this truck for six years and it has never failed me. I'll have it checked out.

Thanks again,

Bob Allen

 

sounds like your converter is unlocking on you.though i wrote this up in the diesel section,you'll find it just as helpful.
it's something quick and free to inspect anyway;

https://www.ford-trucks.com/forums/1...s-harness.html

pay no attention to the 2 digit codes (yours will be 3) nor the early pack plug replacement (you'll need the proper year) nor the year range for the solenoid pack should you find a failed solenoid (again,you'd require the proper year for your truck.)
the basic fundamentals will help you.just use it as a guideline is the point.

 

Thanks. I'll look into that too.