Manual Transmission Oil

[Teqp]

I am about to change my transmission gear oil. The manual says to use API GL-4 75W-90 gear oil. Is it OK to use API GL-5 80W-90 gear oil?

Thanks for the help.

[NismoPC]

Do not use GL-5 specific gear oil. There are some GL-4/GL-5 gear oils that are safe but the GL-5 gear oil will destroy the synchros in SR20 trannies over time. Not a good thing.

Go here for more info: (Several posts on gear oil.)

http://www.sr20deforum.com/search.ph...der=descending

I recently did a clutch job and used Valvoline Hypo GL-4 Specific 80W90 Gear Oil. Seems to work fine.

[Teqp]

Thanks for the information. I spoke with the Infiniti dealer in my area and he said that GL5 was what they use in the shop. Soooo, I went ahead and used Valvoline GL5 80W 90 synthetic blend.

I just put that in yesterday.

Do you know where I can purchase GL4 oil? My local Pep Boys doesn't sell any.

Thanks for the response.

Phil

[NismoPC]

Yea, the Infiniti and Nissan dealers here use the same Castrol gear oil as well. I also read that some Synthetic gear oils that say GL-4/GL-5 are also safe and do not have the chemicals that eat at the synchros.

But, here is what Pennzoil has to say about GL-5:

2. What happens if API GL-5 gear oil is used in an API GL-4 gear oil application?

API GL-4 and API GL-5 products typically use the same extreme pressure (EP) additive system, with the API GL-5 having about twice the concentration of a API GL-4. In service, these additives become active under extreme load and temperature when the protective oil film can be squeezed away. EP additives work by forming wear-resistant compounds with the metal of the gear tooth surface. As the gears mesh, these compounds shield the gear teeth from direct metal-to-metal contact that would cause wear and damage to the gears. If too little of the active additive is present, proper protection would be compromised. Too much of this additive could cause excessive chemical corrosion of the gear surface. If an API GL-5 gear oil is used in a application where API GL-4 gear oil is called for, chemical corrosion of "yellow metal" components may occur, such as bronze synchronizers, brass bushings, etc. This may lead to shifting difficulties or shortened equipment life.

I picked up 2 gallons of Valvoline Hypo GL-4 directly from a Valvoline lube shop for $10 + $4 for a gas can. They poured it out of a 5 gallon container they had in the back, new and unopened. I got lucky.

[Teqp]

Thanks for the info. I decided to go with redline MT-90. I found a local shop that sells it. I will replace the fluid this weekend. After reading those post that you referred to, I decided it was worth the $ to change the oil.

Thanks.:sun: