If it is a rod bearing you should be able to hear it when you rps peak right B 4 you change gears. And yes you can change them with the engine in the truck.
![pssssss :psss:](https://board.marlincrawler.com/Smileys/marlin/psss.gif)
BTW I would put mains in it while I was in it and heck it woludn't hurt 2 put a oil pump in it 2. Thats what I need 2 do 2 mine shortly