The Stovebolt Site Forums The Shop Area Driveline Transmission Oil Additives

After blowing up my original '37 3spd I pieced together a replacement transmission. I'm ready to reinstall but was wondering if there was anything I should add to the gear oil?

I know that engines use additives like zink for break-in and posi-differentials benefit from additives beyond what you get with gear oil, but what about transmissions?

I like Hyper Lube as additive for the manuel transmissions We used their products at work in motor gear boxes and tramissions for jitneys-lift trucks and it made the shifting so much smoother when shifting. For an example I had my 62 4sp. gear box about to replace syncros when I dumped the hyper lube in and they got me through until I tore the truck down to restore it. We used to have gearboxes go out during the middle of the season and the first year we made the complete run with out a gear box failure. I think that says some thing about their product.
62Blue
Don

Originally they were designed for straight mineral oil. I like synthetics. I have been using synthetic in my over the road trucks for over 20 years. In an older vehicle I would recommend something like this http://www.redlineoil.com/product.aspx?pid=46&pcid=7 rather than using additives.

Thanx for the replies!

I did find out that my trannie requires GL4 and not GL5 gear oil. I see that the RedLine product is GL4. I will have to research the Hyper-Lube product.

This is critical for longevity as the GL4 is low-sulfur and not as corrosive on the brass bushings common to this type of transmission.

Thanx again!

~rocker~

Don't use any additives, modern gear lubes have the necessary additives to provide proper protection and lubrication.

Crenwelge I forgot about the Redline products as they are very good.
62Blue
Don

Magfarm51 and DonG summarize the two points of view that predictably show up whenever oil additives are discussed. One point of view is that the major lubrication product manufacturers, with their labratories and staffs of scientists conducting ongoing research, offer the best oils and greases that exist.

The other point of view is that better products exist but the majors are withholding them but they are available as additives. Stuff like STP, Marvel Mystery Oil, etc.

I am not a lubrication engineer but I have read the results of generally accepted lubrication testing procedures for evaluating the effectiveness of lubricants. The test I'm familiar with is two steel balls rotating in opposite directions and forced together under pressure while being lubricated with the product being tested. The wear on the balls is then measured.

I have observed the results of various oils used by myself and others in 2-stroke premix fuel, mixed at various ratios, because I was an off road motorcycle racer in AMA competition riding 2-strokes built by Bultaco, Suzuki, Husqvarna, Honda and Yamaha. The results of using relatively inexpensive oils from the major manufacturers to expensive oils from the "Microbrewers" are intersting.

This is another one of those science versus faith arguments that will probably never be resolved but is interesting to listen to.

I appreciate your perspective Ray, and it's all for the sake of learning ;-)

One thing I discovered in my research was that strong warning by many to use GL4 gear oil - a formulation that was made for early transmissions. However, there are some products on the market that advertise themselves as being GL4 AND GL5 compliant.

Now how can it be that one manufacturer strongly recommends against using GL5, and another says (in essence) "use either one".

My original question about additives was inspired by the concept of "break-in" which I know we do with engines, but I am not familiar with gearboxes.

As it took me 8 months to cobble together a replacement transmission I would prefer not to have to do this again anytime soon!

Thanx again.

Hi Rocker. I also have a cobbled together transmission in my '36 Chevy pickup. It was assembled from new parts from various sources in the early 1970s. Right off the bat it was noisy in first gear. I disassembled it and replaced the new first gear from Republic Gear with a good used gear from GM and the noise was gone. The next problem is that it did not shift smoothly from 2nd to 3rd once it was warmed up. That problem persists to this day evcn though all new parts were used except the first gear and the end play of the synchronizer parts is shimmed to the precise middle of the .025"-.035" specified end play. It is better with more viscous oil, presently "600W" from The Filling Station, but not really working properly.

I recently picked up a complete transmission from a car and I will either put its innards into the case I have now or more ideally find an empty case to use so I can leave the present trans intact. The case I'm looking for was used in '32-'33 "Eagle" or "Master" cars and in '34-'36 pickups. If you might know of one out there the casting number on the case is 590532.

I'm hoping that a set of gears that has been together forever gets along better than a "cobbled together" set.

In the 50 years that I've been interested in this hobby I've never heard of a "break in" period or procedure for a transmission, but we learn every day.

As for GL4-GL5, I read the information on the containers. I've also read that the substance in GL5 that can harm brass can only do so at high temperatures that are unlikely to occur in a transmission.

GL4 and GL5 are not interchangeable. GL4 is the highest rating for gears. GL5 contains EP additives for hypoid rear end gears. These EP additives contain sulfur which is harmful to copper and brass at any operating temperature. The transmissions originally were designed for straight mineral oil, which means it has no additives. EP or Extreme Pressure lubricant or hypoid lubricant was developed for hypoids. GL4 is a much better lubricant than the old gear boxes were designed for in the first place. As for break in period, I have never heard of a break in period for transmissions.

"Break-in" period was a poor choice of words for me. Perhaps I should have said break-in procedure instead.

My concern (apparently unwarranted) was whether there was any special consideration to the bearings, gears and the U-joint when placing a new or rebuilt 30's era transmission into service.

I'm not going to immediately go our and race the machine, but I do want to give it a good launch.

...took sick over the weekend and had to postpone installation. ;-(

Here's another of the endless GL-4 - GL5 articles.

http://forums.nicoclub.com/gl-5-transmission-fluid-t312877.html#p3367628

As ususal, there are amateur opinions on both sides. I wish an active PROFESSIONAL lubrication engineer with a major lubricating oil company (NOT somebody with a single product they're pushing) would weigh in on the subject with an in-depth description of the issue, and the science behind it.

My father started selling lubricants in the 30's. I am 67 years old and still sell lubricants. I have been to lots classes and and seminars over the years. I am careful not recommend brands I sell. I do not sell Mobil, but I think they have a good answer to the question. http://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/GL-5_and_GL-4_Gear_Oil.aspx

Thanx for that link!

It adds a consistency to the argument that GL4= Appropriate for usage in applications where "yellow metals" (brass, bronze, copper) are involved, and GL5=appropriate for all other applications such as differentials and current production transmissions.

It makes sense and would also explain why someone marketing an oil product for current applications would claim compliant for both standards - if no transmission manufacturer uses yellow metals anymore. Anyone aware of the use of yellow-metal for friction surfaces in modern transmissions?

Crenwelge, thank you for posting that link. I found it inconclusive because it does not go into depth about the interaction of "yellow" metal and GL-5. I would like to know what actually happens, under what conditions and how long it takes.

On a Sta-Lube GL-5 SAE 85W-140 container I have the following is stated."For complete fill or topping off of manual transmissions, hypoid type differentials, limited slip/twin grip/trac-loc/sure-grip differentials where 85W-140 grade is recommended"

On a Valvoline GL-5 SAE 80W-85W-90 container I have the following is stated. "For use in manual transmisions and in both regular and limited slip differentials"

That suggests that GL-5 IS OK for manual transmissions.

Can a lubrication engineer or chemical engineer shed some light on this for us?

Total recently purchased Lubricants USA, a company whose products I marketed for many years. All of the engineers that I knew for many years retired at the sale. However Total has contact information for lubrication engineers on their website.
http://www.total-us.com/lub/lubusa.nsf/VS_OPM/A6D73F35BFF19C4DC12572B100537B38?OpenDocument

More on GL-5 from a Mercedes site:

http://www.benzworld.org/forums/unimog/1358944-gl4-vs-gl5-gear-oil-plot.html

Here's part of what it says:

"When I first heard this GL-4/GL-5 corrosion thing, I did some research on the oil co web sites. I couldn't find anywhere that said it was harmful, so I sent a tech message to the Amsoil tech guy. His response stated the history of how that myth got started by the ignorant VW people. When GL-5 first came out it was indeed corrosive to brass syncros. But only at temps above 250ºF. Now since it is impossible to get any street driven gear oil to that temp (It is hard to get engine oil that hot!), there will be no problems using regular GL-5. However, just to satisfy the ignorant masses, the API came up with another added rating, called MT-1 which is tacked onto the end of all GL-5 oils you can buy today. With this MT-1, GL-5 oil is not corrosive at any temp."

Until a lubrication engineer or chemical engineer chimes in, we will be reading endless "crackpot" (amateur rather than professional) opinions.

I am a professional engineering geologist and I can only shake my head and roll my eyes at some of what I hear on subjects like climate change.

Here's some more info/opinions:


http://www.ratwell.com/technical/GearOil.html

yar, the API did not come up with the MT-1 rating to satisfy the ignorant masses. It is a rating of gear lubricants required by Eaton/Fuller and Meritor for use in their class 8 non synchronized truck transmissions. It is not meant for passenger or light truck transmissions. I have been using API MT-1 fully synthetic 50w in my Fuller and Meritor transmissions for about 20 years.

Hi Crenwelge. This subject is very interesting to me because I have always found trensmission function facinating. I don't know if you have ever looked into a motorcycle transmission, but they have a completely different way of synchronizing gears, using dowels called "dogs" that protrude from gears that slide and engage into slots in gears that don't slide.

Anyway, back to MT-1. It is my understanding that MT-1 designates GL-5 lubes that are safe for use with yellow metals. Do the big truck unsynchronized transmissions have yellow metals in them? If not, why would the transmission manufacturers specify MT-1?

How does the 50W that you use compare in viscosity to various gear oils?

I have a '71 Dodge van that I bought new and I have adapted a 4-speed New Process model 445 top loading trans into it to get improved gear ratios for towing. Chrysler specifies 50W motor oil for that trans and I found that viscosity in racing oil.

My Stovebolt is a '36 Chevy pickup that seems to shift best with so called "600 weight oil" that I get from The Filling Station. I understand that "600 weight oil" is similar in viscosity to 160 that is no longer available. Do you know if that is correct?

I would watch out using motor oil in a tranny. If your tranny calls for 50 wt tranny oil yea but nig difference between tranny oil and motor oil.

Big truck transmissions have no synchronizers and no yellow metal. However, with the higher torque ratings of electronic engines which came of age 20 years ago, transmissions were developed to handle them. I am in the Texas hill country and I set my engines at 1450 ft. lbs. torque. However they are capable of putting out 1850 ft. lbs of torque. The MT-1 is fully synthetic and it is pours almost like Mobil 1 15w50. However, it does not get much thinner when it is hot. Our transmissions all have pumps and an oil cooler in front of the radiator. When we still ran mechanically injected engines, we ran 90wt straight mineral oil in them. GL5 would make them very difficult to shift. I don't think it hurt anything, but the drivers would sure complain if someone put in GL5 by mistake. I am not familiar with 600 wt oil nor 160 wt. We used to run 140 wt GL 5 in our rear ends in the summer and 90 in the winter. We now run 80w140 fully synthetic and never change it. I run 50 wt fully synthetic in some of my old jalopy transmissions. I don't think it hurts anything, but it is really too slick for the synchronizers to work properly. That doesn't bother me because I am accustomed to shifting without a clutch any way.

Many late model transmissions call for 50 weight motor oil, usually in a full synthetic. The NV4500 is an exellent example of this, it not only specifies 50 weight synthetic motor oil, but also a specific brand (Castrol) which is fully noted with part numbers on the PTO cover on the right hand side of the transmission case. Use of anything else will destroy that transmission.
It should also b noted that many modern manual transmissions use ATF3 (Dexron3/Mercon2) as the factory fill.