I lost track half way thru that sentence structure.
Let me try and interpret. Typing on a phone is difficult for a lot of folks and I have learned phoneeze.
His 2006 developed a vibration 3 years ago when he had 140K miles.
When he drained the fluid, it had a shimmer to it.
Both carrier bearings were falling apart due to being low grade bearings.
He changes his differential fluid every 50K with GM fluids.
He replaced the bearings himself with a friend and it was difficult so he recommends paying someone to do so it’s done correctly.
I think that’s what was meant.