Transfer case oil

[willystexas]

My M38A1 has been moth balled for over 20 years. So, I am slowly going through it (before I ever try to start or drive it). So, far I am encouraged by its condition. Anyway, I drained the transfer case oil, and I found the oil to have some metal flakes in it. I believe it may be brass. I have no idea how many miles this old oil has on it, but I bet that it is a lot. I would prefer not to pull it until I perform a full restoration at a later date. However, I would like your advice about how much wear is "normal" on these transfer cases. If you saw this oil come out of your transfer case, how worried would you be? Here is a pic.

Old Transfer Case oil

TransferCaseOil.jpg (206.75 KiB) Viewed 2388 times

[Joe Gopan]

Give it a short drive to warm it up and change the gear oil. These chips are residue from day to day wear. The Lube Order change interval is 12,000 miles or annually. Your gear boxes may just be overdue.
Use a Gear Oil rated for both GL-4/GL-5 . NAPA Stores carry it.

[Cabin Fever]

I use NAPA GL-1 90wt (NAPA Part #65-201)

I was told this gear oil is most like that originally used and does not negatively effect yellow metals.

[willystexas]

Thanks for the info

[Joe Gopan]

I use NAPA GL-1 90wt (NAPA Part #65-201)

I was told this gear oil is most like that originally used and does not negatively effect yellow metals.

________________________________________________________________
Check the 50's -60's Factory Service Manual for the 40's-50's UNIVERSAL, CJ-@A thru CJ-5 Jeeps. GL-4 SAE-90 was the specified Lubricant at the time for Differentials and Transmission/Transfer. Today's GL-5 Rated GO sold by NAPA, Lubriplate, is rated GL-4/GL-5 and suitable in the transmission.

[raymond]

Ah, the old GL5 vs non ferrous yellow metals question. I've been in the oil business my whole life. You can run GL5 oil in a transmission with copper or brass, or bronze parts without hurting it provided the oil meets the MT1 spec or passes the ASTM D130 copper corrosion test with a rating of 1B or higher. What you see in that oil is metal that was removed mechanically. If it was removed via the sulphur compounds in gear oil, it would have been done chemically and you would not see a metallic sheen in the oil, but rather a greenish/black sheen from the sulphur oxidizing the bass/copper. And beware of anything that lists GL1 through 3 as a gear oil rating since the API no longer recognizes or even tests for this specification. My best advice would be to use a GL5 with the MT1 designation, a ASTM D130 of 1B or better or listed as safe for "yellow metals." If in doubt, contact the manufacturer. They would rather sell you something correct for the application than you have an adverse effect on your equipment. Any company that doesn't have that information available for it's oils is one to be avoided.

Here are some interesting links for gear oil specs. I've always thought the 4 ball weld test and the Falex pin test are kind of cool
http://www.grattaoil.com/wh/A-Study-of- ... -Lubes.pdf
http://www.machinerylubrication.com/Rea ... p-gear-oil
http://www.machinerylubrication.com/Rea ... lubricants

[willystexas]

Here is the oil that went into the differentials. (Purchased at Napa) It is labeled GL-4. Here is the manufacturer link. http://crcindustries.com/auto/?s=SL24229

Napa sells a GL-5 gear oil. http://www.napaonline.com/Catalog/Catal ... 0006410049

I will get it for the transfer and transmission. I will put a thousand miles on the jeep, then change them all again.

Raymond, Interesting report on oil.

Thx,
mw

[Cabin Fever]

Napa sells a GL-5 gear oil. http://www.napaonline.com/Catalog/Catal ... 0006410049

I will get it for the transfer and transmission. I will put a thousand miles on the jeep, then change them all again.

Does this GL-5 gear oil also meet the MT1 spec? If not, I would suggest not using it in your TC and tranny.

[willystexas]

I have checked the CRC website, and I was unable to find any MT1 test results for the Sta-Lube Gear Oil manufactured by CRC and sold by Napa.

So, that begs the question, if I am worried about the “yellow metals” in my drivetrain, what should I be using?

Referencing the 2007 study, “A Study of Automotive Gear Lubes” (as recommended by ramond), there are a several good choices available, and a couple of potentially corrosive choices.

NOTE: I have approached the aforementioned study with a dose of skepticism. (Since the study was commissioned by Amsoil, and wouldn't you know it, their product proved to be the best general GL-5 lube tested.) Anyway, I checked several other trusted blogs, and I found this report seems to be the “gold-standard” in “yellow metal friendly” testing (pardon the pun). For more details check: http://www.bobistheoilguy.com/forums/ub ... er=2554764

According to the study:
Top three best “yellow metal friendly” gear oils:
1) AMSOIL Severe Gear 75W-90
2) Mobil 1 Synthetic 75W-90
3) Red Line Synthetic 75W-90

Bottom three (possibly corrosive) “yellow metal friendly” gear oils:
12) Mopar Synthetic 75W-90 with Mopar LS additive
13) Royal Purple Max-Gear 75W-90
14) Lucas 75/90 Synthetic

Not a recommendation, but food for thought.

[Marty, SoCal]

One thing to consider about the EP GL-5 use in a transmission is that the EP hypoid gear lubes don't allow the syncro clutches to grab as well which effects the shift quality. Not much of an issue with the t-case, though.

Redline MT-90 has worked well for some guys on the MB forum. It's made for transmissions, not hypoid rear axles

Big rigs use a 50 weight manual transmission oil. It's yellow metal safe, and good for syncro operation. The 50 weight is rated on a different viscosity scale than the gear oil scale, it's basically the same viscosity as 90 weight. Unfortunately, it's hard to find in small quantities. Some trucks allow the use of straight 50 weight engine oil. I'm going to try 50 weight Valvoline VR-1 racing oil in my GPW's T84.

[Cabin Fever]

This is what I use in my TC/tranny. It's GL-1 rated, 90w mineral gear oil.
http://www.napaonline.com/Catalog/Catal ... 0410679149

According to what I could find at NAPA, there are three gear oils that meet MT-1 specs:
http://www.napaonline.com/Catalog/Catal ... 0006411620

http://www.napaonline.com/Catalog/Catal ... 0006411620

http://www.napaonline.com/Catalog/Catal ... 0006411620

I have found this discussion helpful:
http://www.willysmjeeps.com/v2/modules. ... pic&t=4340

[raymond]

Be careful with API GL1 through 3 as the API no longer supports nor tests for certifying these oils. In most cases, the equipment used for certification of oils of these 3 classes no longer even exists.

GL3 was originally the spec for synchronized manual transmissions, but it is now defunct.

The designation API GL-3 denotes lubricants intended for manual transmissions operating under moderate to
severe conditions and spiral-bevel axles operating under mild to moderate conditions of speed and load. These
service conditions require a lubricant having load-carrying capacities exceeding those satisfying API GL-1 service
but below the requirements of lubricants satisfying API GL-4 service.

MT1 was not originally intended for manual transmissions with synchronizers, it was a spec to address a different problem.

The designation API MT-1 denotes lubricants intended for nonsynchronized manual transmissions used in buses
and heavy-duty trucks. Lubricants meeting the requirements of API MT-1 service provide protection against the
combination of thermal degradation, component wear, and oil-seal deterioration, which is not provided by lubricants
in current use meeting only the requirements of API GL-4 or 5.
API MT-1 does not address the performance requirements of synchronized transmissions and transaxles in
passenger cars and heavy-duty applications.

However, it became apparent that the additives used in MT1 spec GL5 have more or less solved the yellow metal compatability problem that arose out of the abandonement of GL3 Here is what the API has to say about using GL5 MT1 oil in place of GL1 .

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.
API GL-1 lubricants are generally not satisfactory for most passenger car manual transmissions. However, these
lubricants have been used in some truck and tractor manual transmissions. Lubricants meeting service designation
API MT-1 are an upgrade in performance over lubricants meeting API GL-1 and are preferred by major commercial
vehicle manual transmission manufacturers. In all cases, the transmission manufacturer's lubricant quality
recommendations should be followed.

http://www.api.org/certification-progra ... l-2013.pdf







Bottom line, use GL4 or GL5 with MT1 spec oil and you will be just fine. GL4 has become increasingly hard to find, especially if you prefer a synthetic oil. Thus the increasing popularity of synthetic GL5 MT1 oils. If you can't find the MT1 spec, see if the oil in question passes the ASTM D130 Copper strip corrosion test with a 1B or better rating. MT1 oils are required to do this. And don't be afraid to call the oil manufacturer with technical questions. They are happy to answer them and would rather sell you a product that is satisfactory then something that damages your equipment.

The following site contains a short explanation of the ASTM D130 copper strip corrosion test.


http://www.machinerylubrication.com/Rea ... es-effects

Raymond

[raymond]

P.S. Non MT1 GL5 gear oil will not immediately destroy copper alloys. What happens is that the non buffered sulphur hi pressure additives in standard GL5 oxidize copper alloys 1 layer at a time in the surfaces coming into contact with each other resulting in greatly accelerated wear. In other words, there will be no immediate catastrophic failure. Instead, you will not get near the life expectancy. It is these sulphur compounds that give gear oil it's distinctive smell. MT1 oils "buffer" the acidic effects of the sulphur.

Raymond

[willystexas]

ramond,
Good info to know. It is interesting to learn about the science behind gear oils.

Due to my proximity to a NAPA auto part store, I have investigated their gear oil products. Thus, I have contacted the manufacturer of "Sta-Lube" (CRC Industries) gear oils. In particular, I asked about their ASTM D130 test results and their MT1 compliance. Here are the two products in my request:

1) Sta-Lube GL-4 Multi-Purpose Gear Oil (85W90) Part # SL24229
2) Sta-Lube API/GL-5 Plus New Generation Heavy Duty Limited Slip Gear Oil (75W90) Part # SL2462

I received the following response from CRC Industries:

Dear Sir:

Our gear oil products are yellow metal safe, they meet 1B for the ASTM testing.

Regards,

CRC Technical Support
Phone: 800-521-3168
Email: techservice@crcindustries.com

Thanks for the help.