My 91 F150 will not shift and stay in 3rd or OD. Took the truck and had the tranny flushed and filter changed. Only thing this did was when I am running in 2nd at 3300rmp at 55mph and I back off the throttle, it shifts down 2 gears to about 1100 rpm, but when I step back on the gas, it jumps back to 3300 rpm. Inbetween there is no power applied to the drive shaft, it just waits till it hits the 3300rpm and then accelerates again. This just started and I am at aloss if it is the tranny or a torque converter problem. Any help would be greatly appreciated. The place that did the flush said it should have fixed it as it seemed like a pressure issue...

 

Is this an AOD transmission? If so, I would check the TV rod connection and make sure it has not come loose at the throtlle body. If this is intact, it sounds like you might have lost the bushing in the rear of the trans, in which case, it's time for an overhaul.

 

Yes it is AOD, and on the steering column I have 1, D and OD, it never actually shifts to D or OD unless I back off the gas then it drops down like it is shifting.