1993 Ford Explorer overdrive

Hello
Need to understand the revs 500rpms?
Do you mean it revs 500 above what it is turning in 3 before overdrive? Possible torque covertor lockup switch going haywire.
Is MIL /check engine light on?
Let me know
Thanks for donation

There are no dash lights on, the check engine light will come on after it idels for awhile but goes out again when driven. The reving occurs after shifting into overdrive and the tach goes from about 1500 to 2000 and back down repeatedly

The rpm flucatuation is caused by the torque convertor locking up droping rpms like it should then droping out back to Dr.. The cause could be the lockup switch in valve body or the teflon sealing rings that holds fluid pressure to the clutch in convertor have failed due to non use. Have you tried new fluid and filter? Maybe some trans flush could help then new fluid and filter. If you keep going say up to 65 + does is stop fluxing?

I tried changing fluid and filter with no results. I was considering some Trans-X. The slipping still occurs at 65 but not quite as pronounced. How hard of a repair is the lock up switch? thanks for all your help

Drop pan the switch screws into valve body just pull off wire and unscrew. Very common part to fail . That's why I asked if it was less at higher speeds it is better so that takes the torque convertor and valve body out of possible problems.