The Stovebolt Site Forums The Shop Area Driveline Gear lube in 53 3600 3/4 ton truck

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

The SM-420 holds about 6.25 pints of SAE 90 Mineral Oil.

Here's what I use...

https://www.tractorsupply.com/tsc/p...-all-mineral-90-transmission-fluid-2-gal

Mike B

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

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.

This is what you use in your rear...GL-5 Hypoid Gear lube rated for extreme pressure.

https://www.tractorsupply.com/tsc/product/traveller-80w-90-gl-5-gear-oil-6-1-quart

Sold everywhere, not pushing Tractor Supply, their links are easy for me to find to give you the specs.

Mike B

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

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

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

Thanks for the info on diff fluids and the link to what Tractor Supply sells.

The shop in my hometown in Southeast Texas that only rebuilt rear axles swore by using non-synthetic 85-140 in rear axles