# Isssues about Manual Transmission gear oil



## chacono (Oct 30, 2004)

Folks. I have a '97 4wd(LSD), manual 5spd, extended cab HB. Lately the transmission whines when I put it gear first thing in the morning which I believe is caused by low oil in the transmission. My issue is related to the GL designation of the gear oil. The owner's manual states that 80w-90 GL-4 should be used but I have not found GL-4 anywhere. The oils that I have found all are 80w-90 GL-5 (castrol, exxon, lucas). 
Would I cause harm to my transmission if I change the transmission gear oil with 80W-90 GL-5?

Thanks in advance.


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## Yontrop (May 14, 2004)

I believe that GL-5 is bad for the brass in the synchros.


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## skramer360 (Aug 14, 2005)

Napa has GL-4 oil. I bought some there when I changed mine.


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## chacono (Oct 30, 2004)

Thank you gents. I did manage to find GL-4 oil but I have yet to find an explanation as to why GL-5 oils would be harmful to the transmission. 
Regards.


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## Benji97XE (Oct 8, 2007)

My understanding is that GL-5 spec oil contains sulfur additives that eat away at the brass in our syncros.


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## thorn87d21 (Jun 2, 2007)

Im getting ready to dump the GL-5 soon just to be safe but I do know that I had a transmission fail on my previous 2000 Hyundai Elantra after using GL-5 in it which Hyundai was known to use plastic syncros so if GL-5 can eat away at brass just imagine what it can do to plastic lol. I had grinding in 1st through 3rd after about 30-40,000 miles of using the GL-5 in the Hyundai. Was it failure just of age or was it the fluid I dont know but the thing ran fine until I started using the GL-5. Go figure.


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