So i have a 89 ford f150 4x4 302 auto when the truck shifts into 3rd and over drive, the truck begins to shake badly. i have done plugs wire cap rotor fuel pump checked the timing, checked all drivelines it has newer tires all around they have been balanced. so i have come to transmission failure, although i am not sure what has failed in the transmission. any advice would be appreciated. thank you

 

Welcome.

What I do know, when an AOD goes into DRIVE(3rd), it is direct drive. It is not driven through the converter(like any other common automatic). It basically drives directly off the motor, thus there is no slippage from the converter. I'm guessing your transmission is just plum wore out and the clutches are not holding.

How many miles? When/if ever has it had a fluid/filter change? Typically the fluid will break down and cause chatter when shifting. But if it is just worn out it won't grab enough at all. Thus the chatter/shake you are feeling. Does it go away if you ease off the throttle?

Is the TV cable hooked to the throttle linkage? If that breaks loose it will not tell the transmission to boost pressure to hold the clutches under acceleration. Typically it just slips badly under any throttle application.

 

Could be the engine too, does it shake bad when stone cold or only once the engine gets to operating temp?