GM 14-bolt FF Rear End with 149k miles

Thanks guys for the responses. As usual, I've gotten an education on this thread. I'll let my friend at Chevy do a full inspect of the diff and bearings and replace any parts needed, and then fill it with full synthetic as prescribed by GM for that VIN. And I'll also ask him about the Astro. He put something in it to help the chatter and bumping sound that would happen on slowing down. That has gotten better but its not completely gone. Now I'm wondering if he really put in an additive or if he may have just drained it and filled it with synthetic.

And like MarkW8 mentioned above, I've seen the GM G80 RPO around for so long and on so many websites that I've seen it also listed as positraction and limited slip among several other terms. Its great to finally find out what the G80 is in the trucks. From my reading last night some say the G80 RPO still may be limited slip in the cars (not trucks). Confusing for sure. I hope the G80 locker in our '97 2500 burb hasn't been damaged with the additive.

Thanks again to all,
Marty