Squealing noise in the drive shaft

I have narrowed the source of the noise to where the drive shaft meets the rear diff. Only does it when in reverse. When rolling backwards and I kick it Ito neutral the sound goes away.

 

I have a similar issue with the sound coming from INSIDE the driveshaft. I replaced the 3 U joints and the carrier bearing. The squeaking sound persists as if its source is the driveshaft itself maybe 8 inches to a foot forward of the rear differential. I was unaware that the driveshaft itself had zerk fittings on it until some people mentioned there being 8 different ones on the previous page, so i'll try that next. I REALLY dont want to have to get a new rear driveshaft for a fucking annoying squeak... But its driving me insane.