GM 14-bolt FF Rear End with 149k miles

MartyW wrote:
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

Posi traction was just a marketing name for the limited slip system used in older GM cars. GM was one of the first companies that came out with a limited slip option, for it's older cars.

The name 'posi traction' or as it was commonly referred to as 'posi' became a generic term for any limited slip, starting from what I remember in the 1960's. I was a drag strip rat back in the 1960's, so I come by my info 'honestly'. :B

The name 'posi' became a generic or common or popular, term for any traction control system, whether it was a GM, Ford, Mopar. Also whether it was in a car or truck. Of course, this common usage of a marketing term for all traction control systems, became confusing.

Then GM truck line was one of the first light trucks to introduce a locker. The G 80 Eaton Gov Lock. But people still referred to the Eaton Gov-Lock as a limited slip, when it wasn't. It was and is a locking axle that locks up and provides power to both wheels, in a traction limited situation.

I think back then, light truck competitors like Dodge and Ford were using Limited slips.


It was just like the generic word for any and all photocopying, became Xeroxing even if you were using an IBM or Ricoh photocopier, for example., I think this happened, because Xerox corporation and machines were early photocopy machines. Kind of like the GM marketing name...posi traction.

I note, there is a lot of confusion between how a locking system works, how a limited slip system works and the differences. I note BenK has outlined the differences very well.

I have also noted some techs are unsure also. No one can be an expert on everything and that is why I second the suggestion that a GM shop manual for the vehicle in question, needs to be consulted and as a result, the correct information about maintenance will be confirmed.

Hope this helps,

Les