Gl-4 Sae 80 Source...and Even Needed?

TSM calls for GL-4 SAE 80 Gear oil for my T15 and D20. Doesn’t seem to be much out there any more though. Anybody find/use a specific one, and is synthetic ok?

I read a few articles that say avoid GL-5 due to soft metal digestion but that seems to be the bulk of what is available today. Haynes says use GL-5 so another head scratch moment.

 

Sta lube makes a gl4 gear oil

pn 24239

 

This is what you want. LOTS of discussions about this in past posts! The Sta Lube is on Amazon and it's usually available at NAPA.

 

That's what I run in my T-15s. I purchase from Amazon - https://www.amazon.com/CRC-Sta-Lube-SL24239-Multi-Purpose-Hypoid/dp/B000M8RYMC

WalMart 85W90 GL-5 in axles.

 

Use the GL-4 anywhere there is yellow metal (transmissions, etc).

Don't listen to the counter guys who say "this stuff is the same." And certainly don't listen to the haynes robots.

 

And I'd also point out that all the Borg-Warner 3-speeds (T-84, T-90, T-86, T-14, T-15) share oil with the transfer case. You should run the same oil in both units.

 

This is safe for our transmissions, right? I've been using it for a few years now.

Traveller Ford Tractor All Mineral 90 Transmission Fluid, 2 gal. at Tractor Supply Co.

 

I would not. The Jeep manual says GL-4. That's GL-1.

API Gear Oil Specifications - oilspecifications.org

"The designation API GL-1 denotes lubricants intended for manual transmissions operating under such mild conditions that straight petroleum or refined petroleum oil may be used satisfactorily. Oxidation and rust inhibitors, defoamers, and pour depressants may be added to improve the characteristics of these lubricants. Friction modifiers and extreme pressure additives shall not be used."

My emphasis.

 

Would GL4 be recommended for a Ford T18 as well? I have never been able to find GL4 so I have been running GL5 for the last 3 years...

 

GL-4 is recommended and should be used. They are much easier on the blocking rings (synchronizer rings) and typically shift better with GL-4. NAPA carries it in Sta-Lube brand. It is available online as well. Some Walmart stores carry it and some old time parts houses do. Most parts houses can order it if they can be bothered.

 

Valvoline MTF is also GL-4, O'Reillys auto parts usually stocks it. I use this in my Nissan.

Valvoline™ Synchromesh Manual Transmission Fluid

 

I tripped over a gallon of this same stuff for 10 years debating whether it would be fine to use in our transmissions. I finally dumped it at the oil recycler this year.

I only know that it was 10 years because before I dumped it, I asked the same question you did. And then I searched, and found I had asked the same question 10 years prior, lol.

I think gl-1 would be fine in the jeep transmissions, but for the price of gl-4, why chance it. Apparently, the original mb's and gpw's used gl-1 in the transfer case/transmission, or so I heard.

As others have mentioned, sta lube gl-4 is the best bet for keeping your synchros in good shape and having smooth shifting.

 

I wouldn’t use that in any of the BW Jeep gearboxes talked about... that’s a modern day lubricant.. much thinner than 90wt..
Prob fine for your Nissan, but I would be running a MT90 in a tranny like that...

I know this horse is beat, but there is only one lubricant readily available on the market for the older BW style gearboxes...

Sta lube gl4 gear oil
pn 24239

Like we should make this a sticky and stop talking about it... maybe get them to be a board sponsor...

 

This. And well said.
Beat to death. Well documented. On the same level as knuckle pudding and flat towing.