• To ALL forum users - As of late I have been getting quite a few private messages with questions about build ups here on the forum, or tech questions about your personal project. While I appreciate the interest, sending me a private message about these topics distracts from, and undermines the purpose of having a forum here. During the day I wear many hats as a small business owner-operator and I work tirelessly to provide the absolute best service possible to you, our valued customer. When I created this forum I rounded up some of the best minds I knew so that any tech question you might have could be asked and answered by either myself or one of my highly experienced moderators, this way the next time this same question is asked the answer can be easily found and utilized by the next IH enthusiast having the same question. This allows me the freedom to run the day to day operations of the business and minimize the impact to shipments and shop activities that these distractions can cause. It is of the up most importance for me to complete the daily tasks in order to best take care of you our customer, all the while providing you a forum to get the level advice and input you have come to expect and deserve from the premier IH shop in the country.

    So with that I ask that anyone with a question about one of our build ups or a general tech question to please use the forum as it was intended. I am absolutely available by telephone to answer your questions as well but at times may direct you back to our website to better field your question or questions. Most other private messages I will be glad to answer for you.

    Thank you for your understanding.

    Jeff Ismail

Gear Oil: A Commonly Overlooked Lubricant

DF Sales&Marketing

Oil Tech Moderator
a refresher course for many,
an enlightenment for most others

Gear oils are classified by the American petroleum institute (api) using gl ratings. For example, most modern gearboxes require a gl-4 oil, and separate differentials (where fitted) require a gl-5 oil. It is important that purchasers check the oil against the vehicle manufacturer's specification to ensure it does not contain any aggressive chemicals that May attack yellow metal gear components. Sulfur containing ep additives can cause corrosion problems in gears with parts made of bronze, brass and other copper alloys.
Gl-4 rated gear oils do not have the additives which would attack the yellow metals in transmissions and transaxles.
Gl-5 rated gear oils, for the most part, contain the highly sulfurous additives for more protection in heavy-duty differentials. However, there are some lubricant manufacturers who choose not to use those highly active sulfur/phosphorous compounds and thus are compatible with yellow metals. If you have an application which calls for gl-4 and plan on using a gl-5 for more protection, you must be assured that the product you are considering will not damage the equipment.

Api viscosity ratings for gear oils are not directly comparable with those for motor oil, and they are thinner than the figures suggest. For example, many modern gearboxes use a 75w90 gear oil, which is actually of equivalent viscosity to a 10w40 motor oil, 90w gear oil is the equivalent viscosity as 50w engine oil. Multigrade gear oils are becoming more common; while gear oil does not reach the temperatures of motor oil, it does warm up appreciably as the car is driven, due mostly to shear friction (with a small amount of heat conduction through the bell housing from the engine block).

api gl categories

Api category gl-1 (inactive*)
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-2 (inactive*)
designates the type of service characteristic of automotive type worm-gear axles operating under such conditions of load, temperature and sliding velocities, that lubricants satisfactory for api gl-1 service will not suffice.

Api category gl-3 (inactive*)
designates the type of service characteristic of manual transmissions and spiral-bevel axles operating under mild to moderate to severe conditions of speed and load. These service conditions require a lubricant having load-carrying capacities greater than those that will satisfy apl gl-1 service, but below the requirements of lubricants satisfying the api gl-4 service.

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. Lubricants qualified under u.s. Military specification
mil-l-2105d (formerly mil-l-2015c), mil-prf-2105e and sae j2360 satisfy the requirements of the api gl-5 service designation. Gl-5 oils contain as much as 50% more additives than gl-4 oils.

Api category gl-6 (inactive*)
designates the type of service characteristic of gears designed with a very high pinion offset. Such designs typically require (gear) score protection in excess of that provided by api gl-5 gear oils. The original api gl-6 test equipment is obsolete.

Api category mt-1
designates lubricants intended for non-synchronized manual transmissions used in buses and heavy-duty trucks. Lubricants meeting api mt-1 provide protection against the combination of thermal degradation, component wear, and oil seal deterioration which is not provided by lubricants meeting only the requirements of api gl-4 and api gl-5.

this specification released in 1995 combines the performance requirements of its predecessor (mil-l-2105d) and api mt-1. Mil-prf-2105e maintains all existing chemical/physical requirements, stationary axle test requirements, field test requirements and data review by the lubricants review institute that were required under mil-l-2105d. It also adds the stringent oil seal compatibility and thermal durability test requirements under api mt-1. Mil-prf-2105e has been re-written as sae standard j2360. Sae j2360 standard is a new global quality standard that defines a level of performance equivalent to that defined by mil-prf-2105e, a u.s. Military standard for approval that was not available to oil blenders in all parts of the world. It includes all of the most recent axle and transmission testing requirements identified in api gl-5, api mt-1 and mil-prf-2105e including the need to demonstrate proof-of-perform-ance through rigorous field testing.

* api categories gl-1, gl-2, gl-3 and gl-6 were declared inactive by sae technical committee 3 in 1995, even though oils May be marketed with these designations. Similarly, astm does not plan to maintain the performance tests associated with these categories, as in a number of cases these tests can no longer be run because parts or test installations are not available.

Extreme pressure additives, or ep additives, are additives for lubricants with a role to decrease wear of the parts of the gears exposed to very high pressures. They are also added to cutting fluids for machining of metals.
Ep additives are usually used in applications such as gearboxes, while aw additives(antiwear) are used with lighter load applications such as hydraulic and automotive engines.
Ep gear oils perform well over a range of temperatures, speeds and gear sizes to help prevent damage to the gears during starting and stopping of the engine. Unlike aw additives, ep additives are rarely used in motor oils. The sulfur or chlorine compounds contained in them can react with water and combustion byproducts, forming acids that facilitate corrosion of the engine parts and bearings. Ep additives typically contain organic sulfur, phosphorus or chlorine compounds, including sulfur-phosphorus and sulfur-phosphorus-boron compounds, which chemically react with the metal surface under high pressure conditions. Under such conditions, small irregularities on the sliding surfaces cause localized flashes of high temperature (300-1000 °c), without significant increase of the average surface temperature. The chemical reaction between the additives and the surface is confined to this area.
The early ep additives were based on lead salts of fatty acids ("lead soaps"), "active sulfur" compounds (e.g. Thiols and elementary sulfur), and chlorinated compounds. During the 1950s the use of lead soaps was eliminated and replaced by zinc and phosphorus compounds such as zinc dithiophosphate.

swepco gear oils prove the best

Swepco 201, 203, 210 and 212 gear oils far exceed the specifications of gl-4, gl-5, mt-1 and mil-prf-2105e and can be used in most manual transmissions, transaxles and certain differentials. They also contain additives which include:
*oxidation, rust and corrosion inhibitors
*pour point depressant and anti-catalyst
*anti-foam inhibitor
*extreme pressure additive, anti-wear inhibitors and suspension grade molyb-denum disulfide (203 & 212 only)
*adhesive/cohesive characteristics
*limited slip characteristics
*climbing action (201 & 203 only)
· ·swepco 201 gear oil is available in 80w90, 90, 140 and 250 weights. The 80w90 and 90w are commonly used in automotive applications.
· ·swepco 203 gear oil is available in 90, 140 and 250 weights, it is the same oil as 201 with the addition of suspension grade molybdenum disulfide to enhance the ep shock protection, especially for heavy-duty and some off-road racing applications.
· ·swepco 210 gear oil is a “true” 80w140. It has more protection than straight weight oils and reduces heat. It is also “race proven.” 210 can replace many straight weight oils.
Swepco 212 gear oil is the same as 210 with the addition of molybdenum disulfide to enhance the ep package
Another excellent article dick! I've been sold on swepco oil since I switched from mobil one to swepco 306 in the ls 7. It runs smoother, quieter and gets better fuel milage! The 308 in the diesel also runs better and gained 3mpg on the highway!
Thanks for educating us!
I'll be looking for some gear oil for another "project" I have, in the near future.
Hello sir,
it's been awhile ...

I was recommending your 210 80/140 gear oil to someone and they asked me if it contained zink. I told them I don't think so because zink would be detrimental to the yellow metals in their manual transmission. Did I tell them correctly or did I mix everything up?

I tried to go looking up the info on your web site, but I did not understand the only related info I could find. What does the following mean?
Copper corrosion, 3 hrs @212°f (astm d130) ............ 1a
I would think copper corrosion should be zero?

Also please comment on this:
" it is not intended to be substituted where oem recommendations call for single grade 80w or 90 weights. "
why? And don't all our old specs call for straight 80 or 90 w gear oil?

Finally a recommendation ... Please put a link on your building products web site to your oil lubricants part of the web site. Somehow I started out on your building products web page and even generic product searches such as "oil" would not bring me to your lubricants part of the web site. And with no links, it was very frustrating trying to navigate from your building products to your lubricants page. I didn't even know you had a building products division.


DF Sales&Marketing

Oil Tech Moderator

I tried to reply and everything I entered was lost somehow. I don't have time to respond now, but will get back to you later in the day.


DF Sales&Marketing

Oil Tech Moderator

thanks for giving out a recommendation for using swepco 210 gear oil. You are correct when you told them it does not contain zinc. But you might be confused as to what causes problems with yellow metals, it is formulas which have highly active sulphur-phospherous compounds, which are used by a lot of other lubricant blenders. Those oils should never be used in transmissions unless you are sure of the formula.

In regards to the copper corrosion test, it May very well be that in a “perfect world,” zero might be the optimum reading, however it is impossible to meet and the rating of 1a is very favorable.

The comment you quoted about not being intended for use to replace oem recommendations for single grade 80wt or 90wt oils has only been added recently, it probably would not be the correct oil to use in industrial gear boxes which call for straight weight oils. It also does not follow suit with the recommendations of many of our salesmen who have instructed applications for the 210 use to replace those straight weights (myself included). 210 has always been recommended for use which require more protection than the average automotive use. It is used primarily in heavy duty, high performance applications from racing to off-road equipment, even when the oem spec calls for straight 90wt gear oil. The reason I recommended 210 to IHPA over 10 years ago is because Jeff wanted to offer the best oil for the applications, and one that could be used in all of the boxes to keep it simple. Since we do not know what the owner uses his IH vehicle for, it was decided to go for more protection instead of the standard automotive type gear oil.

Swepco does manufacture those other oils, they are: 201 gear oil available in 80/90, 90 & 140 weights, 203 moly gear oil (same as 201 except with molybdenum for more protection in shock applications), 202 synthetic 75/90 (a new product). But keep in mind that the 210 is a true multi-graded gear oil and not to be confused with other products which fall under 85/140 which is a 140 weight oil with a slug of pour point depressants to make it pour like an 85 weight when it is cold.

Your recommendation on the company website is noted, but in all reality, if you would have clicked on “lubricants” instead of “building products” to start with, you would not have had the problem you experienced.

Hopefully, these explanations will answer your questions.
another question if you don’t mind.
From my understanding swepco 210 gear oil is a 80w140 multi-weight gear oil great for most transmissions in addition to transfer cases, axles, etc. And it can be used in any manual transmission calling for a 90 weight gear oil. But what about odd transmissions calling for a much lighter/thinner oil? I’d like to quote two old-time IH heavy truck mechanics and have you tell me which oil I should use in my loadstar’s 5-speed transmission based on their experience.

the owners manual will tell you to run 50 wt synthetic gear oil or 30 wt engine oil. 90 wt or thick oil won't get into the gear and main shaft areas. These 5 speeds turn the low and reverse main shaft gear at countershaft speed all the time. What this means the gears shift off the bottom gears and just basically spun with the shaft. On these trans the gears stay on the countershaft gear and shift with a locking collar. When in any other gear they spin on the main shaft at insane speed. The oil it calls for in the manual is there for a reason and I believe it is 30 wt engine oil. Synthetic 50 w will work also. If you don't believe me try gear lube and when you are looking for a trans to replace it later good luck. They are getting hard to find and parts are not out there any more. Been down this road a few times.

back in the mid 70's on the IH built 5 speed of the time yes they were having issues with lubrication. 90w was too heavy an oil and was not getting where it was suppose to go. They did go to 30w engine oil and added a street ell to raise the oil level up. There was also an additive they added to the oil to help with wear. Have no idea what was in it. At the time the dealership I was at brought in a transfer truck from a near by dealer; it did not make it to our place by about 4 miles. It had gone 30 miles before it seized up and it was full of oil. I believe it was the t495-t496 series that was doing it.

So what oil do you recommend for my odd transmission? Apparently I can’t use 210’s 80w140 as it’s much too thick and I should be using a 30 weight oil, not an 80 weight or heavier oil. And I can’t use 306’s 15w40 engine oil as my 30 weight transmission oil because it contains zink.

DF Sales&Marketing

Oil Tech Moderator
There seems to be a little confusion about how "viscosity" equivalents are different with gear oil and engine oil.

50wt engine oil has the same viscosity equivalent as 90wt gear oil...period!

I have the viscosity equivalents chart in pdf version, but I am having trouble posting it, but believe me 50wt engine oil is right smack dab in the middle of the 90wt gear oil range. If I figure out how to attach from a pdf file, or if someone can tell me how to do it, then I will include it with another post.

Engine oil does not provide the same protection for transmissions, etc. As gear oil does, the chemistry is different. When transmission manufacturers recommended 50wt engine oil, it was also noted that it should be a non-detergent oil.

So, with that said, if you still think that 90wt gear oil, or even the 210 true multigraded gear oil would be too heavy, it doesn't leave much of a choice for you except to get 50wt non-detergent engine oil - which is not available as a swepco product. Options would be: swepco 711 - 50wt synthetic manual transmission gear oil, or swepco 202 - 75w90 synthetic gear oil for your transmission application... The synthetic versions might be a little easier to shift when cold than the 210 would be. The smallest size available would be in 5 gallon pails.
there seems to be a little confusion about how "viscosity" equivalents are different with gear oil and engine oil.

50wt engine oil has the same viscosity equivalent as 90wt gear oil...period!

. . .
[/quote ]

I thought viscosity was viscosity, regardless of the purpose of the oil . see, I'm learning . . . .

But what is the equivalent to the 30 weight not 50 weight engine oil (see my above post)? That's what he was saying to use per the 40 year old specs. Does 210's 80w140 specs easily encompass the equivalent of 30 weight engine oil?

Is there any difference, other than viscosity range, between the 711 and 202 oils? Perhaps I should go with one of these as it does get cold here in the winter ... Down to -15*f here last winter. What is the shelf life after a bucket of synthetic oil has been opened, and use life, of the synthetic oils? Old specs called for changing the oil every ten thousand miles - but in the past its lucky if I do it once every 5 years for my manual transmissions. Perhaps if I had a 5 gallon bucket of oil I'd do it more often.

I do intend to change the seals in the trans. Should they ideally be different or made of a different rubber for 711 or 202 synthetic oil vs 210's oil? My catalog shows seals can be ordered in several different materials. But if I use the IH seal, it was designed long before they ever heard of synthetic oils.
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DF Sales&Marketing

Oil Tech Moderator

the swepco 711 50wt synthetic transmission fluid is rated as a gl-4 fluid. It would be closer in fluidity of a 50 wt crankcase oil.

The swepco 202 - 75wt90 synthetic gear oil is rated as a gl-5 fluid (but can be used in earlier recommendations).

With the specific applications and ambient temperatures you have mentioned, I would go with the 202. I don't know how much oil your transmission holds, but I would be surprised if it is any more than a gallon or two at the most, so 5 gallons would probably be good for two drain/fill applications.

Because of the fact that technology has changed tremendously, I cannot say how long any product would last unless an analysis is performed. However, with over 30 years of experience selling swepco products, I can tell you that the life expectancy in service should be greatly enhanced.

IH did not have a synthetic recommendation because it was not readily available at the time your truck was made and some of the earlier seals did leak using "regular off-the-shelf" products.
See the tech sheet (which I hope is attached) for seal compatibility.

To answer your other question about where 30wt engine oil falls in the gear oil equivalent, it would cover mid 80wt to mid 85wt. You can see the difference in equivalents in the viscosity equivalents chart which is attached