My friend has an 02 Blazer and it has a limited slip differential, BUT i looked though his RPO codes in the glove box and it says it should have a GU6 (open 3.42lol), it does NOT say G80. But i saw it with my own eyes there is a limited slip in there. I think the previous owner put a new axle in, but be says that twards the end of prodution or what ever, they would just throw in what ever parts that are lying around to use them up. But if they did wouldnt they change the RPO code before it leaves? So is that true, or is he blowing smoke out his @$$? lol

 

I can't see GM just tossing random left over parts in a vehicle & NOT updating the RPO. That's BS in my view, he's fogging out his rear more than Seafoming your blazer.

 

rofl!

 

I know back in the 70s GM would run out of certain parts & use what they had but it showed on the line sheets. I bought a new 1979 CK20 4x4 with a 250 hp 350 from the factory. The standard 350 for the trucks was I believe 190 hp. It had a steel gear set, mid high rise manifold. I went to re-curve the distributor & it was already re-curved. I knew a guy that worked in Fremont were it was built & he took the line sheet & it had a 350 / 250hp used in Buick's. It was an end of year production model & they ran out of the truck 350s.
So I would not rule out anything myself. I have seen some different things in my years as a mechanic that sure seemed strange.

 

GU6 does not mean it is open, did you check all codes? Mine has the one saying 3.73 GU4 I think, and G80.