I have a 1999 Ford F150 4.2L Auto with 160,000 miles on it and up till now, no real problems. When the engine is cold and going between 50 & 60 MPH on a level or slight grade the transmission shifts in and out of overdrive rapidly. This only happens when the accelerator is steady and constant not when accelerating. After about two miles, the rapid shifting disappears. I disassembled the Mass Air Flow sensor and cleaned it but no change. I changed the transmission fluid and cleaned the filter about 35,000 miles ago. The fluid is at a proper level also. I would appreciate any assistance on this matter. Thank you.

 

This is difficult to offer any opinion on.
Are you sure it's going in and out of OD?
Reason I ask is because the trans has a temperature sensor that keeps OD from engaging before the fluid comes up to about 90 to 100° +/- in the valve body casting area.
If it is intermttant, the OD lamp should flash.
Otherwise there may be a bad coil pak causing a missfire.
None of these actions have anything to do with the mass air meter.
You should have a look for any code set using a 'good' scanner and not a low end reader.
Good luck.

 

Check your brakes out as well. Make sure nothings dragging. It doesn't take much at that speed.

Good Luck.