GM Rear Lube question
Thread Starter
Racer
Joined: Sep 2012
Posts: 259
Likes: 6
GM Rear Lube question
I have a 1971 Convertible with I don't know which rear differential? It's a 4spd. and a 400sb. My local Chevy dealer has a bunch of morons working in the parts dept. and when I asked for good ole GM rear end fluid and the additive for the rear end the guy looked like a deer in the headlights. Is there an exact name of some kind for the fluid and then for the additive? Also what is the weight of the fluid, is it like 90 weight or 80 or etc.? I think I want to use just the recommended GM fluids.
Thanks for any help
Johnny Y
Thanks for any help
Johnny Y
Melting Slicks
Joined: Jun 2006
Posts: 2,071
Likes: 147
From: S Nevada
They still sell the additive, well at least the local Chevy dealer in my area had it. It's a posi lubricant additive. As for differential gear lube, I rebuilt mine recently and just went with good ole petroleum based Lucas 80-90 gear lube.
I heard the original additive was real sperm whale oil. Not 100% sure on that. Today's stuff is probably a bit more eco friendly.
Yup a quick Internet search confirmed what I thought true. Millions of gallons of sperm whale oil was used in automotive lubricants prior to the 1972 endangered species act. Gotta luv google.
I heard the original additive was real sperm whale oil. Not 100% sure on that. Today's stuff is probably a bit more eco friendly.
Yup a quick Internet search confirmed what I thought true. Millions of gallons of sperm whale oil was used in automotive lubricants prior to the 1972 endangered species act. Gotta luv google.
Last edited by Sunstroked; Sep 19, 2013 at 10:49 PM.
Le Mans Master
Joined: Aug 2010
Posts: 5,339
Likes: 546
From: Central Texas
I stuck with the old sperm whale lube and additive from GM. I know that the part numbers have changed. Someone here surely has the correct numbers though. Or you can buy from one of the vendors here who know what the hell they are doing. I used to be a Chevrolet parts man years ago. It appalls me that these new guys don't know crap. 
Check with Gene @ GM Parts House. I think he hangs out on the C6 forum.
Check with Gene @ GM Parts House. I think he hangs out on the C6 forum.
Last edited by Street Rat; Sep 20, 2013 at 09:39 AM.
Burning Brakes
Joined: Apr 2013
Posts: 926
Likes: 2
From: Castle Rock CO
I used a Full Syn Mobil 1 LS 75/90 Gear Lube and bought the most expensive LS Additive they had on the shelf at the local parts store. Chatter went away after I replaced the gear lube. The old stuff was really gray and dead looking.
You would have thought the computer at the Dealer would be able to pull up the part numbers.
You would have thought the computer at the Dealer would be able to pull up the part numbers.
Race Director
Joined: Aug 1999
Posts: 18,126
Likes: 174
From: WI
I stuck with the old sperm whale lube and additive from GM. I know that the part numbers have changed. Someone here surely has the correct numbers though. Or you can buy from one of the vendors here who know what the hell they are doing. I used to be a Chevrolet parts man years ago. It appalls me that these new guys don't know crap.
Check with Gene @ GM Parts House. I think he hangs out on the C6 forum.
Check with Gene @ GM Parts House. I think he hangs out on the C6 forum.
you haven`t bought posi additive containing whale sperm oil for many- many years at a GM parts counter.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
