Hello, I have a bunch of Valvoline High Performance SAE 75w-90 gear oil and I was wondering if this would be a suitable oil to use in my transmission, transfer case and axles on my 1986 pickup 4x4 with G52 manual transmission. My manual says it recommends 75w-90 GL-4 or GL-5 for both the transmission and transfer case and SAE 90 API GL-5 hypoid gear oil for the differentials or 80w-90 if under 0 degrees.

The back of the Valvoline gear oil says: "Recommended for hypoid differentials (conventional and limited slip) where API GL-5 is specified and non-synchronized manual transmissions where API GL-4 is specified. "

The way I understand it, my transmission isn't a non-synchronized type because those are ancient. Is this still ok to use for the tranny and transfer? Is this oil ok to use in the differentials that call for SAE 90?

If it helps, I'm in the north where the temperatures can become uncomfortable but I'm not too worried at the moment since winter is trying to be over. Thanks for any replies in advance.

 

Nice to see Valvoline has addressed this issue. The long answer would trigger a lot of discussion. I would use GL-4 only in the transmission. A hypoid gear set (differentials) has sliding as well as rolling friction and requires the extreme pressure additives contained in GL-5 oil. These can (arguably) attack the "yellow metal" typically bronze of the synchro mechanism of a typical synchronized gear set. It can be hard to find GL-4 in auto parts places. I got mine at the hardware store. Sta-Lube brand. https://www.crcindustries.com/products/sta-lube.html I would use GL-4 except for the rear axle, where I would use GL-5. The synchonizing action depends on friction between metal surfaces, so many people would not recommend synthetic lube in a manual transmission. Just my $0.02

 

It also says it has limited slip additive. Is that also a bad thing for the tranny? So, it would be ok in the axles but you won't recommend in the tranny. Would that be the same for the transfer? If it doesn't say anything about being synthetic on the bottle can I assume it isn't? I'm not looking for what the absolute best solution to gear oil would be. I just want to know if you think it would be ok to have this in it for the next 30k-60k miles because I bought 10qt of this thinking it was the right stuff several months ago and then my truck became disabled for a bit. Now it's almost recovered and I lost the receipt. I'd hate to spend money again on gear oil and have this stuff just sit on the shelf.

 

What you've got is suitable for everything, but the transmission itself.

 

Yup. That's what I'd do. Since you've got the GL-5, you might as well use it.

 

Cool, thanks for the info guys!