I replaced my rear wiper motor with a NEW unit from Oreilly's $78.00

If the rear window is DRY, the wiper struggles to start a sweep.
After a few seconds, I hit the wiper fluid so I don't burn out my
new motor. Once its wet, it appears to work fine.

I've never had a truck with a rear wiper, is this normal ?

Every car I've had in the past, running the windshield
wipers dry was never a problem.

 

You might have a weak ground on the wiper motor, I would start by checking that. Not sure where its located on the second gen, but it should be back there.