Recently my uncle rebuild the tranny on his 97 caravan transmission shifts okay ,but on high speeds the lock-up feature on the transmission isn't working ,above 60 mph the engine can be heard rev up too high,something it didn't happen before what can be wrong?. engine V6 3.0 transmission 3 speed.

 

Use a scanner, you solenoid pack might not be working.

 

Or when installing the Valvebody, he broke of the L/U solenoid