91 F150 Larriet AOD??
 

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...

On the column it only has 1, D and OD for gear selections, and there is no flashing OD light so I assume this is just and AOD and not E4OD transmission. Do I just need to get a new tranny or rebuild this?? Any help is greatly appreciated.[align=right][/align]