Isssues about Manual Transmission gear oil

chacono · Oct 26th, 2007, 01:52 PM

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.

Yontrop · Oct 26th, 2007, 06:16 PM

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

skramer360 · Oct 27th, 2007, 04:30 PM

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

chacono · Oct 29th, 2007, 08:07 AM

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.

Benji97XE · Oct 31st, 2007, 08:53 AM

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

thorn87d21 · Nov 3rd, 2007, 10:53 AM

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.