T90 oil (GL1)

[garage gnome]

Most people don't realize this, but the T90 cannot take regular gear oil, which is GL4/GL5. The high sulfur content will eat away at the yellow metals in the transmission. You have to look for GL1 oils. Napa has it, but they have to order it in. I found this at tractor supply. It is GL1 and very reasonably priced. Please post other sources for GL1 rated oils on order to help others out.

[Ryan_M]

I buy that same stuff at Tractor Supply here. Also, my local NAPA has 5 gallon pails of GL-1 in stock. I think my first attempt at a T-90 fluid change was such a mess I used all 5 gallons 

[garage gnome]

Ryan, do you still have that picture of the shiny oil? Or was that Randy? I can't remember who posted that.

[aboyandhisdog]

I do find the GL1, GL4 designations confusing.  This Napa GL4 clearly says it is fine for the yellow metals, yet some say you need GL1 only.  My Universal Service Manual spec is for "GL4". 

[aboyandhisdog]

Front shot:

[1955CJ-5]

I use GL-4 in the CJ-5, and was using it in the 3a until I was working out the noise in my intermediate gear and changing oil 2 or 3 times a month....

The GL-4 is about 3 times more expensive.

I would not worry about GL-4 in the jeep transmission, especially since it mentions on the label that it is safe for yellow metals.

Like you I looked in the book and it recommends GL-4..

I like the corrosion resistance and anti-foaming qualities.

My CJ-5 has had who know's what in it over the last 60 years and it's still smoother than the 3a.

I think much of the� yellow metal in oil from the first oil change on a newly rebuilt transmission is just the normal wear-in of parts.

I'd believe the label....the stuff is expensive though!

[bretto]

 My local Napa sells GL1 in gal 65201 and 5 gal 65205.
Tom that nat what you put in your tranny is it?  That's hypoid oil for the diffs.

[Ryan_M]

MacGraham had the really good (or bad...) pic of shiny oil but it's gone now. The rest of the thread is here:

http://www.cj3apage.com/cgi-bin/3Ayabb26/YaBB.pl?num=1363471481/0

[aboyandhisdog]

Hi Brett,� Well, it says it is good for transmissions, and it is GL4 which is what the manual calls for.� How is this not the correct stuff?�

Ryan, thanks for that link - very interesting discussion.  Having read it, I am convinced I am using the right stuff in the Sta-Lube GL4.  I have never seen a Willy's publication that says to use GL1 or straight mineral oil in a 3A. 

[RICKG]

Tom, I copied this response from earlier discussion we had over on the WillysM (M38) site. (Thx Wes K)� It makes good sense.


Modern differentials require hypoid oils because of the heavy gear loading caused by their design. All the other gear boxes have no need for the hypoid quality in their gear oil. Reasoning that should be applied here is "if I do not need it why buy it". Hypoid gear oil is more expensive normaly than straight gear oils. The hypoid oil manufacturers push it's use in all gear boxes for the profit not the need to use it. When the sulpher content got too high in the later hypoids it was determined by many users that it contributed to shorter life of non-ferrous metal. The hypoid manufacturers did not want to lose a market segment so many claim it won't harm non-ferrous metals. They don't prove it they just say it.

 So it's your choice. Pick whatever gear oil you like. I'll stay with a quality regular gear oil meant for regular gear boxes and save the hypoid oil for the proper application , modern offset ring and pinion differentials.

[Quebec Jeep]

I have never seen a Willy's publication that says to use GL1 or straight mineral oil in a 3A.�

I guess back in 1950 the only available oil was mineral....meaning GL1.

This is what i always though.