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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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| | | | Joined: Mar 2017 Posts: 299 'Bolter | | 'Bolter Joined: Mar 2017 Posts: 299 | How many bottles of 80/90 gear lube goes inside of my transmission?
How many bottles do I need to buy??
Thanks guys and gals...
Elmo
Last edited by Elmo; 06/22/2020 9:46 PM.
| | | | | Joined: Jun 2008 Posts: 1,644 'Bolter | | 'Bolter Joined: Jun 2008 Posts: 1,644 | Would I use this same SAE 90 mineral transmission oil in the rear differential?
Chuck
1950 Chevy 1/2 ton (all original)
1951 Chevy 1/2 ton (future streetrod)
1941 Chevy coupe
1938 Chevy coupe streetrod
| | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | Would I use this same SAE 90 mineral transmission oil in the rear differential? NO! You must use gear lube rated GL5 in the rear end. I like 85/140 viscosity. It also holds about 6 pts. George
Last edited by Wrenchbender Ret.; 06/27/2020 4:54 PM.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Jun 2008 Posts: 1,644 'Bolter | | 'Bolter Joined: Jun 2008 Posts: 1,644 | Thanks George. I think I’ll make a trip to Tractor Supply tomorrow to pick up some of your recommend gear lube, then change mine. Haven’t peaked inside the pumpkin in the 12 years I’ve owned the truck.
Chuck
1950 Chevy 1/2 ton (all original)
1951 Chevy 1/2 ton (future streetrod)
1941 Chevy coupe
1938 Chevy coupe streetrod
| | | | | Joined: Mar 2017 Posts: 299 'Bolter | | 'Bolter Joined: Mar 2017 Posts: 299 | Ok now I’m really confused, I’ve heard people say to use a GL5 in the transmission and I’ve heard people use GL4 in the transmission.
Which one is it?
Elmo | | | | | Joined: Aug 2018 Posts: 351 'Bolter | | 'Bolter Joined: Aug 2018 Posts: 351 | Elmo, GL4-rated fluids are recommended for transmissions. They promote smooth shifting and are synchronizer-friendly, especially important for gearboxes that may have "yellow metal," brass/bronze components. The mineral oil recommended by Mike B. is rated GL1, and OK for older transmissions that don't require a higher level of protection. GL4-rated fluids are better products in that regard, but generally cost a bit more. My go-to is Red Line Oil MT-90 which is GL-4 rated, FWIW, since it's what I keep in my shop to service several newer vehicles.
GL5-rated fluids are recommended for wear protection of the hypoid gears used in rear differentials. Once again, FWIW, I use Red Line Oil 75W90 or 75W140, depending on what's called for, and because it's what I have in my shop for the same newer vehicles (BMW, Nissan).
There seems to be a bit of debate in the forum, but the sulfur content in GL5 fluids may promote corrosion of brass/bronze components, and they are generally not recommended for transmissions (which do not use hypoid gears) and so the increased level of protection isn't needed.
Hope that helps.
Doug | | | | | Joined: Mar 2004 Posts: 6,236 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 6,236 | Some of the newer transmission lubes are to slippery for our old transmissions, it doesn't give enough resistance to slow the gears down when shifting which can causes grinding between gears... Mike B  | | | | | Joined: Jun 2008 Posts: 1,644 'Bolter | | 'Bolter Joined: Jun 2008 Posts: 1,644 | Thanks for the info on diff fluids and the link to what Tractor Supply sells.
Chuck
1950 Chevy 1/2 ton (all original)
1951 Chevy 1/2 ton (future streetrod)
1941 Chevy coupe
1938 Chevy coupe streetrod
| | | | | Joined: Jun 2005 Posts: 168 'Bolter | | 'Bolter Joined: Jun 2005 Posts: 168 | The shop in my hometown in Southeast Texas that only rebuilt rear axles swore by using non-synthetic 85-140 in rear axles
Liquidated my projects
Now looking for a decent '47-'55.1 3100, 3600, or 3800
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