E4OD Help

I have a '93 F-350 crew cab 4wd 7.5 with the E4OD tranny. When I shift into drive the truck doesn't move or barley moves. When I switch the overdrive off via the switch on the shifter, which shuts off the overdrive. Everything is fine, except for turning high RPM's especially on the interstate, from not being in OD. Reverse is fine also. Is this a sign of the tranny going south. Or something simpiler?
Thanks


My truck Specs

id take it to a tranny shop that you can trust to not just say that you need a rebuild.

May be a little late on this but try draining all the fluid even the torque convertor and fill back up with Mercon III. Burnt out fluid can cause it to mess up when in overdrive. If it helps a little try doing it again or back flushing if possible.

hanks...Went back to the dealer and he replaced the trany. Was kinda curious, never seen that prob b4. Once again thanks