Which Diff oil..??
Thread Starter
Cruising
Joined: Aug 2011
Posts: 12
Likes: 0
Which Diff oil..??
What diff oil should I be using in my '72...I assume it should be LSD oil with the GM additive but I'm confused by the various grades. I should state that I just bought the car it runs fine but the oil looks like it was a long while ago that it was changed.?
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Which ever gear lube you decide on, wouldn't be in any hurry with the additive, as may not need any. The additive allows more posi slip around turns to quiet things down, but sometimes to much, not making the rear feel like posi anymore. Lot easier adding this this suff later, than trying to take it back out. Been there a few times, and know a few things.
Burning Brakes
Joined: Oct 2001
Posts: 1,241
Likes: 4
From: Okinawa Okinawa
I used mobile one w/ additive but any of the major brands will not let you down. Everyone has their favorites. Just do an advanced search for diff fluid and read through some of the posts and make up your own mind. If you don't believe me, look at the motor oil sticky and you will see 1,000 opinions and everyone thinks they are right.
CF Community Team
Joined: Oct 2004
Posts: 19,355
Likes: 5,240
From: Cape Cod, Mass.
2025 C6 of the Year Finalist - Unmodified
2025 C8 Z06/7/E-Ray of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2021 C8 of the Year Finalist Unmodified
2020 Corvette of the Year Finalist (performance mods)
2019 C1 of Year Winner (performance mods)
2017 Corvette of the Year Finalist
2016 C2 of Year
2015 C3 of Year Finalist
80/90 weight gear oil with one 4 oz bottle of GM posi lube. I've been using that in all my old Corvettes for 42 years and have never had a rear end issue. That's what they were designed to use. Put the posi lube in first, fill it with the 80/90 and then do some figure eights to work it into the clutches.
Burning Brakes
Joined: Sep 2005
Posts: 1,050
Likes: 205
From: Lewes Delaware
80/90 weight gear oil with one 4 oz bottle of GM posi lube. I've been using that in all my old Corvettes for 42 years and have never had a rear end issue. That's what they were designed to use. Put the posi lube in first, fill it with the 80/90 and then do some figure eights to work it into the clutches.
Did the above in my 73 a few months ago and it eliminated the clicking sounds during right turns. Plus the oil that came out verified it needed changing.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
As mentioned before, don't put the friction modifier in, just because other guys automatically do it, because they think it's the right thing to do. I have a C6 ZO6, and the rear end chatters on cold day parking lot tight turns. Lot's of guys just dump in some additive, but not me. Can live with some noisy cold day tight turns knowing I've got got a tight rear diff clutch pack. These cars come from the factory with no diff additive, so just leave it alone. I've let other people borrow the car, and nobody really complains about it.
CF Community Team
Joined: Oct 2004
Posts: 19,355
Likes: 5,240
From: Cape Cod, Mass.
2025 C6 of the Year Finalist - Unmodified
2025 C8 Z06/7/E-Ray of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2021 C8 of the Year Finalist Unmodified
2020 Corvette of the Year Finalist (performance mods)
2019 C1 of Year Winner (performance mods)
2017 Corvette of the Year Finalist
2016 C2 of Year
2015 C3 of Year Finalist
As mentioned before, don't put the friction modifier in, just because other guys automatically do it, because they think it's the right thing to do. I have a C6 ZO6, and the rear end chatters on cold day parking lot tight turns. Lot's of guys just dump in some additive, but not me. Can live with some noisy cold day tight turns knowing I've got got a tight rear diff clutch pack. These cars come from the factory with no diff additive, so just leave it alone. I've let other people borrow the car, and nobody really complains about it.
I also have a C6 Z06 that was making the noise from the rear end. I did a rear end fluid change to the newer fluid with the friction modifier in it. The noise stopped. This was designed for the newer Vettes. Still use the 80/90 with the GM posi lube in the old ones.
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
I guess I'll have to respectfully disagree with you on all counts. The old cars DO need the friction modifier. The longer you hear noise from your rear end the more likely you are to cause damage to the clutches.
I also have a C6 Z06 that was making the noise from the rear end. I did a rear end fluid change to the newer fluid with the friction modifier in it. The noise stopped. This was designed for the newer Vettes. Still use the 80/90 with the GM posi lube in the old ones.
I also have a C6 Z06 that was making the noise from the rear end. I did a rear end fluid change to the newer fluid with the friction modifier in it. The noise stopped. This was designed for the newer Vettes. Still use the 80/90 with the GM posi lube in the old ones.
ABSOLUTELY put it in!
Team Owner
Joined: May 2001
Posts: 87,302
Likes: 1,583
From: Western NY
