D18 gear oil question?

I know this has been asked and answered before, I know I even read the answer I need. Spent over an hour looking for my answer, again, did not find it. Should I use GL4 gear oil only, or is it okay to use gear oil that is rated for both GL4/GL5 ? My brother in-law, was not sure of the oil in the t-case, so changed it and used leftover gear oil from a new gear set-up in his 14' JKU. He put full synthetic GL5 with limited- slip additives in my d18 t-case. I know that do not need limited - slip additives, for the t-case. Will it hurt the t-case? Seems like synthetic would protect better, but I remember that I read that GL5 would not be the best for the bronze bushings or something like that. Am I correct? I did buy some Staylube GL4, but ouch, $34.00? For a gallon? What gear oil should I use, and why?

 

The additives can attack soft metals and cause damage. Synthetic is useable in GL4 usually, but it's probably a waste of money, since the correct viscosity GL1/GL4 mineral oil works just fine.

 

Realize that the transmission and transfer case share oil in the 3-speed Jeeps, so don't put anything into the transfer case that you don't want in the transmission.

I would not put synthetic in either because of likely shifting problems.

You need to work on your Google-foo https://www.google.com/search?q=site:earlycj5.net+GL4+GL5+transmission+oil&ie=utf-8&oe=utf-8

 

last time I need oil I got it from amazon . information said was safe for yellow metals
http://www.amazon.com/Sta-Lube-SL24239-GL-4-Multi-Purpose-Hypoid/dp/B000M8RYMC

 

napa carries GL4

 

I use Redline GL-4 synthetic 75-90 gear oil. I know, expensive but seems to shift a bit smoother.

 

Thanks for the replys. I did buy the gear oil from Nappa, and will change it before driving it again.

 

Thanks timgr,
That did help me find the info. Should help for future searching too!

 

Maybe a sticky with the recommendations for lubricants would be a good idea?

 

Mobil One Synthetic will not attack bronze but....
It is actually a little too slick for some transmission cone clutches (blocking rings)
I've run it in with T-90's and have to shift slow to allow the cone clutches more time to grip.
The main problem with GL1 is that it gets really thick in cold weather.