[roscoFJ73]

Originally Posted by bj74noob

Apparently the lock down function doesn't work (thats what the pros said, not that I know what that means)

Could just be a spring or something.

Ask for a clarification,but its sounds like they mean the torque convertor is not locking up and its a bad spring causing it.
When you get to highway speed the convertor physically connects the engine to the drive so you are no longer using the hydrulic system in the transmission.

Download the free 84-90 body chassis manual and read up the auto transmission fault diagnosis. Im sure it will mention it.

My bet is the trans will have to come out,but they would have mentioned that already