Transmission And Transfer Case Oil

I wanted to change the oil in my transmission and transfer case (standard T-14 & D-18) as I like to do every couple of years. Went to my standard FLAPS to get some 80-90wt G-4 oil. They did not have any only G-5. Went to the 2 other FLAPS in our area and found the same thing only G-5. My understanding is G-5 is hard on any brass or copper in any equipment. My T-14 of course is synchronized with brass parts and so want to keep with G-4. Never had any problem in the past of getting it but I guess all the newer stuff can handle G-5 and so G-4 is not being stocked much anymore. Am I worrying about nothing and G-5 is OK to use, or am I just not looking in the right places to find some? I do know that in my work (oil patch) where they do a lot of testing oil coming out of equipment that they do find brass in G-5 oil and not so much in G-4. I know your can use G-5 in equipment that calls for G-4 as long as there is no brass or copper.
Just wondering what you guys think.

Thanks
Mike

 

This has been covered here before a number of times, in depth if you want the full technical details.

Consensus seems to be - yes, GL-4 does matter. And you can find it by ordering from Amazon, Ebay, etc.

 

I think your on the right track. Defiantly need to stay with Gl-4 oil. I have not been able to find it locally either. If your current Gl-4 oil is not contaminated I would probably not change it. 90 wt oil will likely not wear out for lots of miles. I have thought about draining mine and filter it through some coffee filters or something and returning it to the transmission. Over kill? maybe. but I have gotten to the point I do not throw away anything I remove from my jeep or truck if there is any life left in it at all. You never know when parts of any quality may never be available again.

 

Sta-Lube SL24239

Looks like NAPA isn't carrying it anymore, and you can't get it from Amazon either, but you can get it from a number of places online.

 

Lucas 80-90 shows gl4 and gl5 but it's the same bottle as ever? I'ld expect it to work fine for a transmission...



https://www.walmart.com/ip/Lucas-Oi...5-T&athancid=167869820&athposb=-2&athena=true

 

Just done a search. Looks like most all the gl-4 oils are full synthetic, not sure if they are what we need, also some are listed as gl-5 and gl-4 compatible, humm wonder about this.
I did find on Amazon a 5 gallon pail of sta-lube, gl-4, but it is quite expensive.https://www.amazon.com/CRC-SL24259-...be+gl-4+gear+oil+75w-90&qid=1715819024&sr=8-3
on edit: I also found a non synthetic Gl-4 oil by Mystic https://cdn11.bigcommerce.com/s-yoi...SAE_90_all_products__53008.1683213710.png?c=2
The amazon sta-lube is about 50 dollars a gallon. if you get the 5 gallon pail. the mystic is some cheaper.

 

This is available on Amazon

 

Warren Oil is still making GL-4 85W-90 under their Coastal Brand, which you usually find at farm and ranch stores.

Big R/Tractor Supply Co/Some others can probably still get you Harvest King GL-4, but only in 2 Gallon Jugs https://shiptonsbigr.com/harvest-king-api-service-gl-4-sae-90-gear-oil-2-gallon

Penngrade also still makes it, and has a "Find a Place to buy it" tool https://penngrade1.com/products/gear-lubricants/penngrade-1-classic-gl-4-gear-oil-sae-80w-90/

 

The local NAPA store has GL4/GL5 in stock. A friend has an unopened 5 gallon bucket for $50, but I’m afraid of the GL 5 rating. The NAPA store says its fine for all gear oil applications, but they can’t show me anything that confirms it’s brass-safe. They just look at me like I’m giving them a hard time.
I used to buy GL 4 at Walmart, but they don’t have that any more.
-Donny

 

x2, My napa has the same oil, and the same story.

 

Local NAPA had GL-4 in stock no so long ago.
Need to get a couple of more if so.
Works very well. G-5 is supposed to eat the synchros.

Dave

 

I was in Walmart today looking. Only had GL-5. Sal at Vintage Jeeper just this week posted a test he did with a brass blocking ring soaked in GL-5 for (I think) 6 months. Definite pitting happened. Got me thinking. He recommends the Redline MT90 GL-4.

 

I have been using the 2 gallon Harvest King jugs but Rural King stopped carrying them.

Most recently I bought from Advance Auto. $25/gal. Part no. F990-01.

https://shop.advanceautoparts.com/p/fram-sae-90-gear-oil-1-gallon-f990-01/12399085-P

 

Ebay and Amazon



https://penngrade1.com/products/gear-lubricants/penngrade-1-classic-gl-4-gear-oil-sae-80w-90/

 

The guys at NAPA don't have a clue. Trust me, I used to work there. For differentials, sure, it doesn't matter, in the least, whether you're putting GL4 or GL5 spec oil in them. And for Hypoid Gears, GL5 meets the GL4 spec just fine.

But for manual transmissions and/or transfer cases with brass/bronze components, GL5 can, and will cause damage over time to the brass/bronze components. Don't take the chance. Anything labelled "GL4 Compatible" "GL4/GL5" or "Multi-Spec Gear Lube" isn't going to meet the needs of something that's expecting GL4.

 

This is what I use I dont know if its right Traveller 2 gal. Ford Tractor Transmission Fluid Mineral Gear Oil at Tractor Supply Co.

 

GL-1, which is designated for low stress applications. The GL-4 I used to buy was labelled "EP" for extreme pressure.

API Category GL-1 designates the type of service characteristic of manual transmissions operating under such mild conditions of low unit pressures and minimum sliding velocities, that untreated oil may be used satisfactorily. Oxidation and rust inhibitors, defoamers and pour depressants may be used to improve the characteristics of lubricants intended for this service. Friction modifiers and extreme pressure additives shall not be used.

API Category GL-4 designates the type of service characteristic of spiral-bevel and hypoid gears in automotive axles operated under moderate speeds and loads. These oils may be used in selected manual transmission and transaxle applications.

API Category GL-5 designates the type of service characteristic of gears, particularly hypoids in automotive axles under high-speed and/or low-speed, high-torque conditions.

Wikipedia

 

I also couldn’t find sta-lube locally so I bought and used this.
https://www.amazon.com/Ultralub-Ult...&psc=1&ref_=pd_bap_m_grid_dv_rp_0_13_pr_pr1_i

 

VP Racing Fuels 2703 VP Classic GL-4 Gear Oil, 1 Quart.... Summit Racing

 

Reading this just after I threw some GL4/GL5 in my T86 and D18. Ah well, I’ll be rebuilding the 18 and swapping the 86 anyways. Also I’m guessing that (most) anything is better for the transmission than the half-quart of mud-water that I drained out of it.