So i have just recently rebuilt my manual trans (from a dohc KA) thats mated to my ca. i found that it needed a GL-4 spec fluid for the trans. Upon looking for GL-4 locally i found that its not as easy as it sounds to just go out and get. So i started doing some research and decided on motul gear 300 after looking over tech sheets and talking to the regional sales rep and product specialist. the email i got back from motul states this...
"It was great meeting you. So i did speak with our products specialist and below is what he said.


" I know MOTUL Gear 300 does not harm yellow metals. As I understand it, the GL-5 used to be a problem because when that standard was created base oils used in gear oils were not as advanced technologically as they are now. They were harmful to yellow metals because of the Metal salt content. They are no longer that way and GL-5 gear oils are safe to use on components with yellow metals."

Hope this helps!

Thanks,

Kalpesh Patel
SE Regional Sales Manager



Motul USA Inc. | 790C Indigo Ct. | Pomona, CA 91767

T 909-625-1292 | F 909-625-2697 | Cell 909-538-2093

[email protected] | http://www.motul.com

My main concern was that GL-5 would hurt the yellow metal synchros that our transmissions have. This gave me some confidence in using the right fluid and now my transmission shifts great. if you guys have any questions my knowledge is limited but ill try and help out.

here is the tech sheet


https://www.motul.com/system/product_de ... 1290086772


hopefully this answers some questions but i figured id share my experience for those rebuilding their trans and picking the right fluid to use.

We used to use ATF.

ATF is standard in honda civic transmissions. I wouldn't do it, but it's something to think about.

What I've used in my CA and RB trannies, not in a GTR transmission though.

I just used gear oil. Are you not supposed to?

from what ive read you are supposed to use GL-4. i had been using 75-90 gear oil for some time and always hated the super notchy feeling of the trans so upon rebuilding it i wanted to make sure i was doing everything right and came to this conclusion of using the motul gear 300. the main problem ive seen is the additives that eat away at your yellow metal synchros. you have to make sure the manfacturer states that it is "yellow metal safe". i think gear oil isnt all that bad but it doesnt do the synchros any favors as its not the right viscosity a chemical makeup to allow them to function as well as they should.

After a little hunting, I've found some sources on what oil brands are safe for GL-4 trannys. This guy found files from Amsoil which has supportive data on other oils (although the top oils on the list are all Amsoil, so it may be a tad biased). Sad news is that I got one of the worst oils (Lucas 75w/90) for my tranny just a week ago when I changed the oil. Pisses me off a little. Time to spend another $60 on this s***.

http://www.hdforums.com/forum/sportster ... wered.html

http://xlforum.net/vbportal/forums/arch ... 33539.html

I copied the main info in the post on that link to the Harley Davidson forum so that we wouldn't lose the info (and we're not directing traffic to another site, lol)

FIRST - THIS IS NOT AN OIL DEBATE THREAD
If you want to use Motor Oil, ATF, or cat **** in your gearbox knock yourself out.
If you have a Big Twin, this isn't really applicable to you.

There has been much discussion and debate in the past few years over the use of GL5 Gear Oil in the Sportster Primary/Tranny. This debate centers around warnings that GL5 Gear Oil is corrosive and that it can damage what are known a "yellow" metal parts. Unlike the Big Twins, our Sportsters have a shared primary/tranny and that means that the stator (copper) and clutch spring plate (brass rivets) can be damaged if a corrosive lubricant is used in our application.

The question over the safety of GL5 has been hard to nail down because many of the manufactures will give out conflicting information depending on who you talk to, even within the same company.

WHY is this such a hard question for the oil companies to answer with factual data and WHY is it so hard to find a real answer to the question? The answer is really pretty simple.

Anyone who has spent time studying oil knows about the myriad of various ratings that are applicable for any particular lubricant, from JASO, CF, MIL, etc. The number of different tests that can be done on oil run well into the hundreds, so oil testing by the manufacturer is typically limited to those tests that are applicable to the oils intended use.

So why is it so difficult to get answers to the GL5 corrosive question? It's rather quite simple. Because GL5 is made for use in hypoid gearboxes which by nature don't contain yellow metals, so most manufactures don't perform the standard ASTM D-130 corrosive test on GL5 lubricants.

After quite a bit of digging, it turns out that spAmsoil has actually done ASTM D-130 testing on a number of common/popular GL-5 Gear Oils.

ASTM D-130 ratings fall on a scale going from 1A (least corrosive) to 4C (most corrosive) From a corrosive standpoint, an oil with a 1A or 1B rating is considered safe.

ASTM D-130 ASTM D-4048 FTM-5309 "Detection of Copper Corrosion from Petroleum Products by the Copper Strip Tarnish Test"
A variety of hydrocarbon products including oils, hydraulic fluids, fuel, solvents, etc., can be tested for corrosivity to copper by use of this test. It is limited to products with Ried Vapor pressure no greater than 18 psi (124 kPa). A polished copper strip is immersed in the fluid and heated for a specified time and temperature after which the corrosion is rated by visual comparison to the ASTM Copper Strip Corrosion Standards. The most typical test run is for 24 hours @ 100°C. However, time and temperature can vary according to product type and specification. Results are reported as a number followed by a letter according to the following scheme:

1a slight tarnish a light orange, almost the same as a freshly polished strip
1b dark orange
2a moderate tarnish a claret red
2b lavender
2c multi colored with lavender blue or silver, or both, overlaid on claret red
2d silvery
2e brassy or gold
3a dark tarnish a magenta overcast on brassy strip
3b multi colored with red and green showing (peacock), but no gray
4a corrosion a transparent black, dark gray or brown with peacock green barley showing
4b graphite or lusterless black
4c glossy or jet black

(The ASTM Copper Strip Corrosion Standard is a color reproduction of strips which have the above description.)

The following is the latest product list I could find that has undergone ASTM D-130 testing.

SAFE GL-5 Oils
Amsoil M/T Fluid MTF..5W-30.............. 1A Light Orange
Red Line MT-90.......75W-90 GL4......... 1A Light Orange
Amsoil Long Life FGR 75W-90 GL5......... 1B Dark Orange
Amsoil Severe Gr SVG 75W-90 GL5....... 1B Dark Orange
Amsoil MT & Gear MTG 75W-90 GL4...... 1B Dark Orange
Mobil 1 Synthetic....75W-90 GL5......... 1B Dark Orange
Castrol Hypoy C......80W-90 GL5......... 1B Dark Orange
Castrol SYNTEC.......75W-90 GL5........ 1B Dark Orange
Citgo Citgear Std XD 75W-90 GL4........ 1B Dark Orange
GM Synthetic Axle....75W-90 GL5........ 1B Dark Orange
Pennzoil Gearplus....80W-90 GL5.......... 1B Dark Orange
Pennzoil Synthetic...75W-90 GL5......... 1B Dark Orange
Red Line NS Gear Oil 75W-90 GL5......... 1B Dark Orange
Red Line 75W90 GL-5..75W-90 GL5....... 1B Dark Orange
Torco SGO Syn G LS....75W-90 GL5...... 1B Dark Orange
Valvoline High Perf..80W-90 GL5........... 1B Dark Orange
Valvoline SynPower...75W-90 GL5......... 1B Dark Orange

MARGINAL GL-5 Oils
Delo Gear Lubric ESI 80W-90 GL5.......... 2A Claret Red
Delo Trans Fluid ESI 50W..................... 2A Claret Red

UNSAFE GL-5 Oils
Royal Purple MaxGear 75W-90 GL5......... 4A Trans Black
Mopar Syn LS additive..75W-90 GL5....... 4A Trans Black
Lucas 75/90 Synthetic75W-90 GL5......... 4B Graphite Blk


More information on Amsoil's Gear Oil Testing can be found in this document.
http://www.oilteksolutions.com/GearLubeWhitePaper.pdf

Ah ha! Just thought of using my transmission oil into my diff, that way I don't waste this oil. Brilliant! The things you think of in the shower, lol.

Yea, the dif doesn't have any yellow metals, so nothing to worry about. I'm glad I ended up running Mobil1 in the trans. It's only GL-5 rated, but it came out well in the GL-4 test.

Just use the Nissan Manual Transmission Fluid.

Honda transmissions also use a light viscosity. The older trannies like what are mated to B-series use 10w-40 and the newer ones mated to K-series use "Honda MTF" which a lot of people replace with Amsoil Synchromesh. My Mazdaspeed3 has Motorcraft XT-M5-QS (aka "unicorn piss). Anyways, I guess what I'm getting at is that all these transmissions usually shift like butter. The B-series transmissions are a bit notchier because they use shift rods instead of cables.

Is it safe to run these lighter weight oils in our transmissions? Including the FWD transmissions? I mention this because float said he's used ATF before and that's pretty light weight compared to the 75w-90 that's recommended.

I never said I used ATF in an S13 trans. I meant in my old D-series Civic.

My bad, I meant to say TMS. Looking back I'm not so certain he meant to say he used ATF, but he didn't specify and his post was immediately after yours, float.

Regardless, what may happen if we were to use a lighter viscosity oil in our gear boxes?

Excessive wear. I'm sure it would work in the short term. I also wonder how it might effect the synchros

What determines what viscosity a transmission uses? I understand in engines that bearing clearances and oil pressure play a role, but I imagine transmission don't load the same way nor do they have clearances like an engine nor oil pressure. Transmissions just circulate oil by having the gears sitting in the oil and it transfers as they turn.

i would imagine the viscosity would change how the fluid coated the synchros mainly. In a manual trans my main purpose of the fluid is to lubricate the synchros then the gears. I would think that a lighter weight might not build up between the clearances inside the rotating assemblies within the box. I kind of wish i would have experimented a little before i rebuilt mine now. just to see how it reacted knowing i would rebuild it afterwards. Im by no means a transmission expert but thats what makes sense in my head

mdb4879 wrote:What determines what viscosity a transmission uses? I understand in engines that bearing clearances and oil pressure play a role, but I imagine transmission don't load the same way nor do they have clearances like an engine nor oil pressure. Transmissions just circulate oil by having the gears sitting in the oil and it transfers as they turn.

cadet18 wrote:i would imagine the viscosity would change how the fluid coated the synchros mainly. In a manual trans my main purpose of the fluid is to lubricate the synchros then the gears. I would think that a lighter weight might not build up between the clearances inside the rotating assemblies within the box. I kind of wish i would have experimented a little before i rebuilt mine now. just to see how it reacted knowing i would rebuild it afterwards. Im by no means a transmission expert but thats what makes sense in my head

float_6969 wrote:I also wonder how it might effect the synchros

Exactly. We don't know. We're just guessing. We're just car enthusiasts, and neither drivetrain nor gearing lubrication experts. Unless you are absolutely sure you are smarter than the gearbox manufacturer, or you have someone you're absolutely sure is smarter than the gearbox manufacturer telling you otherwise, just follow the FSM. Viscosity-wise, synchros need a certain viscosity, they need a CERTAIN amount of friction to operate. Too much or too little, and they will not be able do their jobs. If you have new synchros, and a rebuilt transmission, don't overthink it, just use a brand name 75w90 synchromesh oil as per the FSM, as that's as good as it will ever get.

By the by, I've looked around what oil I should use when I did my tranny rebuild, and I could barely find transmission oils, that have GL-4 compliance, but DO NOT have GL-5 compliance. Mostly historical, old stock stuff, or from obscure brands. Most of the run-of-the-mill passenger car oils available today are GL-5 compliant. I doubt any of them eat up synchros, that would be just stupid. If the oil is specifically for passenger car synchromesh gearboxes, BUT has GL-5, it's still good for you. Think about it. FWD is significantly prevalent today. FWDs use transaxles, meaning there's only one oil for gearbox AND differential. They NEED GL-5 load bearing capabilities for the diff, hence the compliance, but they also need to keep synchros intact.

mdb4879 wrote:My bad, I meant to say TMS. Looking back I'm not so certain he meant to say he used ATF, but he didn't specify and his post was immediately after yours, float.

Regardless, what may happen if we were to use a lighter viscosity oil in our gear boxes?

I meant to say that. I have no science to support it, though so DYDD.