I have a 1997 Ford Expedition XLT with the 4.6L V8 that has 217000 miles. It never had a problem shifting until recently. I dropped the transmission pan and changed the filter and fluid. Changed the transfer case fluid. When I drive it now, it will rev the rpms up and then start accelerating. Shift two or three times and hesitate to shift after that but still gaining speed until about 25 - 35 mph before it starts bucking. And the overdrive light flashes on and off. The transmission whines during acceleration and deceleration.
My car has 217000 miles.
My car has an automatic transmission.
As a rule, I NEVER change the transmission fluid on a vehicle with that high of a mileage unless it has replaced regularly throughout the life of the vehicle. Replacing fluid that is thick with new fluid can cause issues everywhere in the trans.
While performing this service, are you sure you replaced the seal to the trans filter and it seated properly without tearing the seal? If the filter did not seat properly it could cause your issue.
Did you fill it with the +F fluid? Is the fluid level correct while running? Fluid level is everything on a trans.
If all of the above is correct, I think either your have some ’funk’ floating around in your trans getting in some of your valve body jamming up some solenoids or the thinner viscosity of the new fluid is not creating the pressure you need due to worn components.
At 217k miles, you may try a flush service or you may need a new transmission. The whining noise is probably the torque converter slipping a bit due to the new fluid (which requires removal of the transmission anyways). If you would like to have a transmission fluid service done, a certified mechanic from YourMechanic can come to your home or office to perform this task for you.