Rear Axle Gear Oil?

KRanger · November 7, 2003

I just purchased a 1999 2wd Suburban with a locking differential, and needed to replace the seal for the right axle. The owners manual calls for GM part# 1052271 gear oil only(no substitutes) and not to add a friction modifier. I went to the dealer to get the oil and they highly recommended the modifier. I don't know if I need it or not? Any advice will be greatly appreciated. Thank you.

Butch 02 Denali · November 7, 2003

KRanger, the recomended oil is a synthetic and is already rated GL5 for positraction. They say don't add the friction modifier because it comes in the oil already. Some add the friction modifier anyway, and that is ok for the G80 locking diff that comes in your truck. Actually the Eaton G80 is a combination locker/limited slip diff.

Butch 02 Sierra Denali

SilveradoWV · November 7, 2003

A few people do get it from the dealer, but its just synthetic. You should be fine using Mobil1, etc.... Like above, the friction modifier is already in what you buy in the parts store, not sure about the GM stuff.

JayMan · November 9, 2003

The G80 is made by Eaton, and it should have Carbon Fiber clutch plates. Although GM recommends their $24/qt synthetic 75W-90, here is what Eaton has on their URL:

"Eaton strongly recommends utilizing an API-GL5 approved Mineral-Based 80W-90 Axle Lubricant and one 4-oz bottle of Limited Slip Additive (GM or Ford). "

They claim a synthetic without proper additives will cause excessive chatter. Check out the cheap 80W-90 stuff at NAPA: It already claims to be for limited slip, so it looks like GM might require more friction modifier?

My first gear oil change, I refused to pay $24/qt for gear oil, so I used some Exxon SGO 75W-90 I had around. The gov-lok stopped working and chattered on wheel slip in snow.

I got the cheap NAPA 80W-90 and 2 bottles of friction modifier, drove around for a week, then put in Mobil 1 Gear Oil (Claims to be for limited slip). Works fine.

KRanger · November 9, 2003

Well, I appreciate the information that you have provided. I replaced the axle seals and filled it up with the recommended fluid. I only paid $5.68/qt so I wasn't unhappy with the price.