Freakin Unreal!!!

[Camino LS6]

As you guys know, I'm replacing the rear in the '92 Blazer.

The trouble is that it is a G80 locking rear and the debate over synthetic/dino oil and additive/no addititve is all over the place.

After reading a zillion different forums, and talking to my friend at the Chevy place, I am no closer to a definitive answer on this.

G80 is a build code RPO and seems to mean different things in different years and on different vehicles.

So I need a definitive answer on a '97 Tahoe G80 (the donor car my new rear is from).

Anyone have a manual for that year?

[Camino LS6]

Anyone?

[loki]

good luck on your search

[Camino LS6]

Thanks, Loki.

A friend on another site just posted the '97 Tahoe owners manual and it calls for 80W90 GL5 gear oil and doesn't mention the additive.

Hope that's right.

[A Horse With No Name]

Sounds right to me, actually Camino.

Chris

[Camino LS6]

You'd be surprised at the range of opinion around the net on this.

I'm going with the manual, at least for now.

[fightingbee]

TSB 76-02-02A from Oct. '98 has a rear diff fluid chart, part of it states:

(After listing the F, Y, B/D, and GMT800 platforms)

"All other limited slip or locking differentials including C/K (non-GMT 800), S/T, M/L, G trucks: Use Only GM P/N: 1052271. (Do NOT add Limited Slip Additive)"

FYI, The GMT800 also does not call for the additive, just lists the P/N 12378261 75w-90 Synthetic Axle Lubricant instead of the P/N 1052271 80w-90.

[daves87rs]

I would go Syn for sure.

I'm going from dex III to Dex VI when I change the wife's ATF on the Cav.

With the wear and tear of city driving, I feel the syn is worth it.

I think the same way about gear oil too.....

[Camino LS6]

According to what I've found, it would be a mistake to use synthetic in any pre-'98 rears as it will eat the seals.

[daves87rs]

According to what I've found, it would be a mistake to use synthetic in any pre-'98 rears as it will eat the seals.

Time to upgrade the rears?

[Camino LS6]

Time to upgrade the rears?

Well, I'm upgrading from a broken rear to one that isn't.

But no, I'm sticking with the Dino oil since the replacement rear is a '97. As for the front, why fix what isn't broken?

[daves87rs]

Well, I'm upgrading from a broken rear to one that isn't.

But no, I'm sticking with the Dino oil since the replacement rear is a '97. As for the front, why fix what isn't broken?

Very true....

[67impss]

I would change the gear oil in the front diff & transfer case if it uses it or the proper ATF . Just my certified :twocents: fwiw. They all have seen the same mileage & abuse plus the big BANG. Lets get the debris out of the units.

[Camino LS6]

I would change the gear oil in the front diff & transfer case if it uses it or the proper ATF . Just my certified :twocents: fwiw. They all have seen the same mileage & abuse plus the big BANG. Lets get the debris out of the units.

That thought has crossed my mind.

Even so, the front diff has only seen a tiny percentage of the use the rear has.

[67impss]

That thought has crossed my mind.

Even so, the front diff has only seen a tiny percentage of the use the rear has.

I take that it's a part-time unit then

[Camino LS6]

I take that it's a part-time unit then

Most definitely, full-time 4wd was never a good idea. It wore parts terribly and killed fuel economy, only a dedicated AWD system works well enough in those categories to be viable. The domestics toyed with full-time 4WD in the 70s, and it was a real loser - many of those vehicles were converted to part-time.