GL-4 and GL-5 Rated Oils

Joined
Oct 3, 2008
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It now seems to be common to find fluids that are rated both GL-4 and GL-5. Having said that, I use both GL-4 (transfer case) and GL-5 (differentials) in my truck. At the moment, I purchase different fluids for each. Would it be wise to stick with what I'm doing, or would it be a better option to just go for the dual rated oils? Thanks!
 
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Feb 1, 2003
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RI
Some GL5's with LSDs additives don't shift too well with manual transmissions. For 'ends and transfer cases, use the best you can afford. You should have no problem using GL5 in mechanical transfer cases. You should NOT use GL4 in rear/front-ends calling for GL5.
 
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Dec 2, 2002
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Washington St.
The older generation of additives used to make gear oil meet the GL-5 spec had chemicals that deteriorated yellow metals (bronze, etc) in transmissions. Newer GL-5 additives don't have that problem, so the gear oils using this later generation of additives can carry both GL-5 and GL-4 labels.
 
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There is a thread somewhere on here about a guy that has a corolla I think and has used many types of GL5 to match the factory fill of GL4.. The conclusion was that after trying all kinds of brands and synthetics that the Valvoline GL5 was smoothest. I have a tranny fluid change coming up in a 2000 celica with a 5 speed and I am going to give the Valvoline a try.
 
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Dec 30, 2006
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Dallas,Tx USA
 Originally Posted By: krismoriah72
There is a thread somewhere on here about a guy that has a corolla I think and has used many types of GL5 to match the factory fill of GL4.. The conclusion was that after trying all kinds of brands and synthetics that the Valvoline GL5 was smoothest. I have a tranny fluid change coming up in a 2000 celica with a 5 speed and I am going to give the Valvoline a try.
I emailed Valvoline one time and they said their GL5 gear oil is perfectly ok to use in a modern synchronized manual tranny. Won`t harm a thing they said........no yellow metal harm at all.
 
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