Transmission And Transfer Case Oil

Just be glad that you can find the correct gear oil for our Jeeps. I’m going through a similar search for gear oil for my ‘99 BMW rear diff. My car has a rarely spec’ed “M Sport 25% lockup” LSD. There is only one gear oil designed specifically for this, and a later “electronically actuated” diff. Its only offered by BMW, and it seems is not stocked in North America. I’ll be ordering probably from Norway, but is also available from Britain, Germany, and Latvia. Shipping costs the same or more than the product from most suppliers.
By the way, my gear oil is supposed to be a “lifetime fill”, which means it lasts a little longer than the car’s warranty. With 25 years and over 100,000 miles, mine’s getting changed.
-Donny

 

Page two of this states that "Almost any diesel motor oil classifies as a GL-3 or GL-4 in gear protection." and "...just about any diesel motor oil can pass the GL-4 gear oil ratings."

Does anyone have insight and or experience on this?

 

I purchased eight one-quart bottles of StaLube 85w-90 GL4 gear oil from Amazon back in March. That supplier no long shows the GL4 in stock but Amazon does show a supplier with eighteen 5-gallon cans of StaLube 85w-90 GL4 in stock: Amazon.com: Sta-Lube API/GL4 Multi-Purpose Gear Oil 85W90 SL24259.

FYI - Back in March NAPA on-line listed several of their locations in a 100-mile radius of Pensacola, FL as stocking StaLube 85w-90 GL4 in both one-quart and one-gallon quantities but none of the locations I went to or called actually had any in stock. One NAPA store manager told me that NAPA would not/could not carry the StaLube GL4 due to lack of availability. YMMV.

Martin

 

I thought GL-1 was actually the stuff we’re supposed to be using and was spec’d for our old slugs.

 

It is what is specified in the manuals, most of which were written long before we had other choices. Some of the GL-4 oils are stated to be safe for yellow metals, some are not. Since I know GL-1 is safe, and will do the job, I see no reason to use something else while it is still available.

 

Well, yes. I once owned a GMC with LSD. The specified 'friction modifier' additive for the diff was whale oil. Truly.

Good luck with that today!

 

My Jeep FSM calls for GL4 in the trans and tcase

 

"My Jeep FSM calls for GL4"

I probably should get a later manual. The ones I have only go up through the late 50s, but 3 of my 4 Jeeps are from the 40s, and there really is not much difference mechanically between a CJ2A and a CJ5. A T-90 is a T-90, and a D18 is a D18. I have always used GL-1 in a T-90, and will use that until I can't get it.

 

Though motor oil might meet a protection spec, you want to run a 90 weight GL4 gear oil in your CJ. I have a car that run sae 30 motor oil, and another car that runs ATF in the 5 spd transmission. For my Jeeps, its either 90 or 140 weight GL4. I can use 140 because temps where I live rarely drop below 70 degrees.
-Donny

 

Supposedly the current Jeep specified fluid for the AX-15 transmission is synthetic 10w-30 engine oil. I suspect this is due to the lack of any suitable gear oil in their supply chain that is safe for yellow metals.

 

Last fall I changed (1970 CJ5) transmission, transfer case, and both front and rear LS differentials with Exon Mobile GL5 85-90 wt. gear oil. I put additive packages in front and rear differentials. I wonder if I used the wrong oil? thanks

 

Gl4 is almost impossible to find reliably local and even amazon is hit or miss on availability. I just get mine from summit racing. I use Driven Racing Oil gl4 conventional, it was recommended by a guy who builds vintage road racing transmissions. Summit also has penngrade for $8 qt

https://www.summitracing.com/parts/jgr-04530

https://www.summitracing.com/parts/bpo-77296

 

I am waiting on a answer from Mobile if their 80 to 90 weight gl5 gear oil contains sulfur compounds. Local distributor says it does not have sulfur in it. I think I can smell sulfur in the oil, maybe I am wrong.

 

What I am using contains sulfur I will have to change with a synthetic oil with no sulfur.

 

Since I put GL5 in it, I guess I need a new transmission now...
And the obvious choice is a 4 speed...

Following that logic, I also need new parts in the tcase...

107:1 CR here I come!*



*As soon as I can upgrade the cooling system on my debit card that is*

 

FWIW, @Vintage_Jeeper just did an experimental video on instagram where they soaked some brass transmission parts in GL5 for a couple months and then looked at em through a microscope. It revealed obvious pitting. I was glad to see some definitive proof against GL5 for our use.

https://www.instagram.com/vintage_jeeper/reel/C64biLkRf2k/

This is what I've been using with good results. I also add 50/50 mix of lucas oil to my trans/tCase.

https://www.zoro.com/sta-lube-apigl-4-multi-purpose-gear-oil-1-gal-sl24239/i/G4612929/?cjdata=MXxOfDB8WXww&cjevent=302b9a33186c11ef813fb7dc0a1cb828&utm_source=CJ&utm_medium=affiliate&utm_term=ps-dns-609bf2fd26e6ca001ebf3d7d-1622529-12455651&utm_content=12738330&utm_campaign=1634220

 

Search our site, especially posts from @nickmil & @timgr for authoritative info on GL5 versus GL4.

Also, although this fellow is a Toyota guy, he explains the problems with GL5 even in modern manual transmissions.

 

I warned my customers when they purchased an old style (T-18,T-14,NP-435,SM-420, T-90, etc.) that if they used synthetic or GL-5 in the transmission the warranty was null and void, that they specifically needed to use GL-4 and told them sources where they could get it. In every, and I mean every case, where there was a warranty claim the customer used the the wrong lubricant. I even had one come back saying we screwed up and found the transmission full of water.

 

Don’t use synthetic. May cause hard shifting issues. Too slick for the blocking rings.

 

Tomorrow I am removing the gl5 oil from transfer case and transmission. Been in there for 7 months. I am replacing with Mobil/Exon fluid 50 manual transmission oil. It is a GL4 rated oil not GL-5. SAE 50 weight oil recommend by Mobiles lab where ever it is at. Ant bodies thoughts?