I am slowly learning about the 4.3L but I am having some shifting issues, I am told its a torque convertor switch. It is constantly shifting from 45-65mph. Today after I washed the truck and was driving it it like lost all power and didnt want to shift then i left off the throttle and pushed it again and it shifted fine. Any help to point me in the right direction would be great!

 

How much is the RPM changing during the events you call 'shifting'? Does it feel like a normal gear change or not as much as a gear change? If it doesn't feel like a full gear change, your torque converter may be locking & unlocking.