AOD severe shift problems after rebuild
1993 FORD AOD transmission (1993 Thunderbird Super Coupe)
- Late / erratic / no upshifts.
- Stubborn downshifts / no downshifts.
- Stuck 3rd gear direct clutch stalls engine when coming to a complete stop.
- Symptoms grow worse after the vehicle is driven for any length of time.
The transmission was rebuilt recently. Here is a list of the parts used:
- Newer 4R70W wide-ratio planetary gear set components, clutches and bands, and new 1-2 accumulator.
- New tail shaft Governor.
- Rebuilt (stock spec) torque converter.
- LenTech street terminator valve body (specifically calibrated for the OEM torque converter and wide-ratio gear set).
When cold, the transmission will shift properly, but not as smoothly as it should. Additionally, the shift points are not consistent (at the same RPMs for any given speed/throttle setting).
It appears that the transmission starts to refuse to shift properly, either up or down, after being driven for a period of time. This results in very high engine RPMs before it will shift, even at very light throttle. Shifts are always very harsh at this point no matter what the RPMs.
Further, when it does reach 3rd gear it seems to stick there, and will stall the engine when the vehicle is brought to a complete stop. Pulling the shift lever back to 1st gear is the only way to force 3rd gear to dis-engage. Once it is in 1st, it refuses to shift into 2nd until engine redline is reached no matter how little throttle is applied.
Along with this, the transmission will not downshift at low vehicle speeds even if the throttle is fully open (gas pedal floored). Clearly, once the transmission is fully warmed up, it stubbornly refuses to upshift until excessive engine RPMs are reached, and will not downshift at all.
Transmission was rebuilt but the stock valvebody was cleaned and re-used. The tail shaft governor was replaced with the rebuild. It displayed all of the symptoms listed above. Next, the tail shaft governor was replaced (again, with a unit supplied by LenTech) and a new LenTech street terminator valvebody was installed. The symptoms remain the same.
I’m at a loss as to what to do next. The transmission shop that originally did the rebuild could not solve the problems, and that’s why I had the governor and valvebody replaced (by the local dealership). Several transmission experts have stated that it’s either a sticking governor or faulty valvebody, but in my case both have been replaced with new components (?). Does anyone have any advice at this point? This has become such a nightmare for me and I’ve already spent a bundle of dough on it… what could possibly be wrong that everyone has overlooked?