Synchromesh fluids and GL-# ratings....

[badtlc]

I have noticed that the synchromesh fluids (RP, Amsoil, Pennzoil, etc.) don't list a GL-# rating. Does synchromesh imply a certain level of protection? It seems most manual transmissions call for a GL-4 level of protection but none of these popular fluids claim to meet that. Am I missing something?

 

[440Magnum]

It actually sorta goes the other way around. Most manual transmissions are allergic to the high sulfur content of GL-5, which attacks "yellow metal" synchro clutches. Most of the "MTL" or "Synchromesh" fluids carry a a GL-4 or lower rating. Rear-end fluids need the extreme-pressure protection of GL-5, but not manual transmissions. Many manual transmissions get a factory fill of ATF so the sulfur is never an issue, but it becomes an issue for those intended to use a heavier fluid. Its gotten hard to find a heavy gear oil that doesn't have too much sulfur for some transmissions. As an example, I own one of the late-production Aisin AX-15 manual transmissions in a Jeep Cherokee. It was built for GL-3 fluid, and as a result the currently recommended maintenance fill (as practiced by Jeep dealerships) is synthetic ENGINE oil. Nominally 10w40 is recommended as a good replacement for 90-wt gear oil (the kinematic viscosities are similar), but I've gotten a bit better results with M1 15w50.

 

[Ken2]

Amsoil 75W-90 manual transmission gear oil is listed as GL-4. Perhaps the gear oils you were looking at are a lower viscosity. http://www.amsoil.com/lit/databulletins/g2077.pdf Here's more than most of us want to know about gear oil specs: https://www.lubrizol.com/DrivelineAdditives/AutomotiveGearOil/GL5.html As the Lubrizol link shows, GL-4 and GL-5 gear oils are suitable for certain differentials. If the synchomesh fluid you use isn't suitable for a differential, it won't have the GL listing.

 

[badtlc]

This is only about manual transmissions, not differentials. GL-5 doesn't apply to these fluids, obviously. I'm asking why these manual transmission based fluids (synchromesh fluids) don't specify a GL-4 rating. Many many manual transmissions specify light fluids but still require GL-4 protection. Some examples of these fluids are Pentosin MTF2, Redline MTL, Fuchs 75W-80 FE, Castrol Syntrans 75W-80 FE, etc. These are all fluids with similar viscosities but the synchromesh fluids don't list if they are GL-3, GL-4, etc. compatible/rated. Why is this? Is it implied that they are GL-4 rated because they are designed for synchronized manual transmissions? I don't get why the seem to avoid saying whether or not they are for use in GL-4 applications given the many number of applications out there that require the viscosity these fluids provide.

 

[antiqueshell]

It certain seems that the big oil companies in the US anyhow seem determined to not clearly offer a GL-4 only gear oil and for the life of me I can't understand WHY this would be. You can look around the world and find MANY major brands with GL-4 rated products which are widely available in the retail market, from companies like Castrol (Castrol Syntrans Transaxle 75w-90 GL-4) Shell Spirax S3 G, and S4 G 75w-90, Pentosin MTF 2 75w, Valvoline Synthetic 75w-90 ect...yet here in the USA a first world nation we can barely find ONE and even that is a throw back to earlier specs. CRC Sta-lube 85w-90 GL-4 which is only available at NAPA which often times has to order it for a customer. This seems to me like some kind of kooky US wide marketing ploy of some sort. I'd like to ask the US divisions of those major companies if they would please offer those products in the US...seems like it would be a simple task, with little issue because I would be willing to pay a bit more for a major brand that has the blessing of car makers like VW 501.50 on it.

 

[gregoron]

Here's an informative white paper on Synchromesh MTF from Molakule: http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1231182&page=1 It also contains a list of GL-4 certified or GL-4 applicable MTFs. This applies to Pennzoil and GM Synchromesh. After my own research on GL-4 applicable MTFs, I'd look for MTF with the synchronizer friction additive instead of just gear oil, pick the right viscosity as per your spec, and make sure it's yellow metal compatible.

 

[MolaKule]

Originally Posted By: badtlc

This is only about manual transmissions, not differentials. GL-5 doesn't apply to these fluids, obviously. I'm asking why these manual transmission based fluids (synchromesh fluids) don't specify a GL-4 rating. Many many manual transmissions specify light fluids but still require GL-4 protection. Some examples of these fluids are Pentosin MTF2, Redline MTL, Fuchs 75W-80 FE, Castrol Syntrans 75W-80 FE, etc. These are all fluids with similar viscosities but the synchromesh fluids don't list if they are GL-3, GL-4, etc. compatible/rated. Why is this? Is it implied that they are GL-4 rated because they are designed for synchronized manual transmissions? I don't get why the seem to avoid saying whether or not they are for use in GL-4 applications given the many number of applications out there that require the viscosity these fluids provide.

If you see my list of dedicated MTL fluids at Dedicated MTL's with GL-4 Ratings they all have Performance Improvement or PI additive packages that give them a GL-4 protection rating, regardless of the viscosity, and regardless of whether or not they explicitly state such.

 

[antiqueshell]

I have been thinking about folks using Sta-lube 85w-90 GL-4 gear oil in their synchronized manual transmissions and have reconsidered this because like MolaKule mentions these other dedicated MTF fluids have special additives that help to protect the soft yellow metal synchronizers, which products like Sta-lube likely do not have.

 

[badtlc]

I guess I'll re-word the question a bit. Ignoring any specific viscosity requirements, are all "synchromesh" type fluids compatible with transmissions that specify a GL-4 fluid?

 

[MolaKule]

Originally Posted By: badtlc

I guess I'll re-word the question a bit. Ignoring any specific viscosity requirements, are all "synchromesh" type fluids compatible with transmissions that specify a GL-4 fluid?

I think I explained this earlier:

Quote:

they all have Performance Improvement or PI additive packages that give them a GL-4 protection rating, regardless of the viscosity, and regardless of whether or not they explicitly state such.

Stated another way, the answer is "YES," they have to be. Here is what application-specific MTLs consist of: 1. Base oils of various types and viscosities to make a specific viscosity and have anti-shear properties 2. GL-4 Performance Improvement (PI additive package) chemistry which consists of the following a) GL-4 anti-wear (AW) additives b) anti-rust additive c) copper and aluminum metal deactivator/buffering agent d) anti-foamant e) special friction modifier (FM) f) dye I don't know how much clearer I can make it. BTW, Application Specific = Dedicated.

 

[badtlc]

Originally Posted By: MolaKule

Originally Posted By: badtlc

I guess I'll re-word the question a bit. Ignoring any specific viscosity requirements, are all "synchromesh" type fluids compatible with transmissions that specify a GL-4 fluid?

I think I explained this earlier:

Quote:

they all have Performance Improvement or PI additive packages that give them a GL-4 protection rating, regardless of the viscosity, and regardless of whether or not they explicitly state such.

Stated another way, the answer is "YES," they have to be. Here is what application-specific MTLs consist of: 1. Base oils of various types and viscosities to make a specific viscosity and have anti-shear properties 2. GL-4 Performance Improvement (PI additive package) chemistry which consists of the following a) GL-4 anti-wear (AW) additives b) anti-rust additive c) copper and aluminum metal deactivator/buffering agent d) anti-foamant e) special friction modifier (FM) f) dye I don't know how much clearer I can make it. BTW, Application Specific = Dedicated.

I get that, but you said it as if you were only positive of the fluids you mentioned. You didn't list every synchromesh labeled fluid out there. That is why I was trying to determine if any and all "synchromesh" fluids are for some reason inherently compatible with GL-4 applications even though none of them mention suitable for use in a GL-4 application. It doesn't make sense to leave that off. How many cars out there just say "use a synchromesh fluid?"

 

[MolaKule]

Quote:

I get that, but you said it as if you were only positive of the fluids you mentioned. You didn't list every synchromesh labeled fluid out there.... It doesn't make sense to leave that off. How many cars out there just say "use a synchromesh fluid?"

I listed the MTF fluids that I have current knowledge of, that is, an analysis that shows the AW package.

Quote:

You didn't list every synchromesh labeled fluid out there

Quote:

It doesn't make sense to leave that off.

And that is somehow my fault???? If some obscure MTF is made in Timbucktoo India I should have that on my list????? If you have a more comprehensive list with analysis, then list them.

Quote:

How many cars out there just say "use a synchromesh fluid?"

I dunno know, but it sounds you have done a survey so you tell us.

 

[badtlc]

I think you took that completely the wrong way. I'm saying your post was written like you were talking only about the fluids you listed. That is fine. It is a great and helpful list but I'm not talking about specific fluids. I am curious about synchromesh fluids in general, not the fluids you are familiar with. I don't get why they call them synchromesh in the first place and not MTLs or MTFs. Does the term synchromesh imply something that requires GL-4 protection? Is this why they don't take time to list GL applications? I just don't get why these companies are not putting this information out there if the fluids provide such protection. I hope you don't think I'm picking you Molakule. I think you took the previous post as a personal shot and it was not.

 

[MolaKule]

Originally Posted By: badtlc

I think you took that completely the wrong way. I'm saying your post was written like you were talking only about the fluids you listed. That is fine. It is a great and helpful list but I'm not talking about specific fluids. I am curious about synchromesh fluids in general, not the fluids you are familiar with. I don't get why they call them synchromesh in the first place and not MTLs or MTFs. Does the term synchromesh imply something that requires GL-4 protection? Is this why they don't take time to list GL applications? I just don't get why these companies are not putting this information out there if the fluids provide such protection. I hope you don't think I'm picking you Molakule. I think you took the previous post as a personal shot and it was not.

OK, but you sounded somewhat accusative. Maybe I mistook your comments. All of the fluids I listed in the link are GL-4 fluids suitable for synchromesh Manual Transmissions. This discussion is about light truck and passenger car Manual Transmission fluids specifically. 1. most Manual Transmissions (except some HD trucks of course) have synchronizer assemblies of brass or carbon fiber construction 2. most manual transmissions have a gearset with a particular type of construction

Quote:

Gearing: Most gear types in manual transmissions are of the helical type, which because of the cut, reduce noise and vibration. Due to their angular cut, thrust loads are transmitted to the shafts on which they reside. The gears on the input and output shafts are usually produced in one integrated piece, called “gear clusters, “ or the cluster gear assembly. You will notice the only gear that is actually moved is the reverse idler gear. This is moved into position to mesh with the small reverse gear on the input shaft so you can “back up” or reverse direction. At higher reverse speeds, this gear will usually give off the familiar “reverse” whine. Lubricant effects: Being in constant mesh, they are dipping in the oil bath and slinging the oil up to the shifter assembly. Since they transmit torque, they must have an anti-wear additive in the lubricant in order to reduce wear. The slipping and rolling action of the gear teeth causes localized high pressures and heating. The anti-wear additive forms a protective but complex ferrous film at the contact surface to protect from galling and other wear mechanisms. Other components such as thrust washers, flat thrust bearings of the roller type, and shims may also need cooling, lubricant film, and anti-wear additives as well.

3. In order to protect the gears, bearings, shafts and shims, a GL-4 AW protection additive is part of the fluid package, hence they carry a GL-4 protection rating. 4. in order to allow smooth synchronizer engagement, a special friction modifier is included. Since the discussion is about light truck and passenger car transmissions, and not HD OTR transmissions, the fluids in these light truck and passenger car transmissions have to have a Manual Transmission "synchromesh" fluid. If this doesn't answer your question, may be you can be more specific and we can go from there. Manual (synchromesh) Transmission Technology

 

[gregoron]

There is Synchromesh that is a brand trademarked by GM, and there is synchromesh which is the generic definition for a synchronized gearbox. I believe that all trademarked Synchromesh you are looking for has to have GL-4 application-specific properties as mentioned above. Some PDS will say GL-4 suitable in them, but they are not advertised as such as Synchromesh is a GM brand and specification (i.e. Dexron). It's up to GM, and those who bottle GM-specific Synchromesh MTL, to set their own specifications - not API. Now, it just happens that you can use this brand for GL-4 specific manual transmission applications.

 

[MolaKule]

Originally Posted By: gregoron

and there is synchromesh which is the generic definition for a synchronized gearbox....

That is very true, greg. We have had this discussion many times in this formum about Synchromesh vs synchromesh and I am surprised so many people have NOT done any searches before or researching before entering into these discussions. Then there is Pennzoil Synchromesh, a brand of synchromesh fluid by Pennzoil, a 9.5 cSt (about 0W30 weight) MTL with a GL-4 addpack. Then there are the GM Synchromesh fluids brand which are 10.5 cSt (about 5W30 weight) MTLs with a GL-4 addpack. I developed this list to assist in the selection of synchromesh-type fluids so please help me understand what is so confusing about it?

Quote:

A. The four MTL fluids closest to a Kinematic Viscosity of 6.1 (About the same viscosity as a DexronVI) or so are: 1. Castrol Syntrans FE 75W, 2. BMW (Pentosin) MTF-LT-3, 3. Honda MTII or MTF 2. 4. Ford FML-XT-11-QDC B. The next higher viscosity MTL would be the 7.5 cSt versions (About the same viscosity as a DexronIII) 1. Royal Purple's Synchromax 2. Ravenol MTF-2 3. Honda MTF 4. VW part number G052512A2 5. GM Manual Transmission and Transfer Case Fluid 6. BMW (Pentosin) MTF-LT-1, 2 C. The next higher viscosity MTL would be Castrol Syntrans V FE 75W-80 8.0cSt D. The next higher viscosity MTL would be BG Synchroshift II 8.2 cSt E. The next higher viscosity is Mopar Type MS-9417 MTL 9.0cSt F. The next higher viscosity MTL would be Pennzoil Synchromesh 9.3 cSt G. The next group of MTL’s are in the 10.x cSt range are: 1. Redline MTL 70W80. 2. Amsoil MTL 3. GM Synchromeshs’ 4. Volvo MTF 645 5. Ford Motor Craft XT-M5-QS H. The next higher viscosity MTL would be: 1. Redline MT-85 – 12.0 cSt I. The next higher viscosity MTLs would be: 1. Amsoil MTG 14.5 cSt 2. Redline MT-90 15.6 cSt 3. Castrol Syntrans Multivehicle 75W-90

 

[gregoron]

Hi Molakule, Sorry, I can't help you understand it anymore as I understand it as is already. Basically, if it's in your list it's safe for manual transmission use - even if the manufacturer doesn't specify it as GL-4. I bought RL MT-90 for my VW Jetta that specifies GL-4 with a 75W-90 weight based on your list. I did do my own research and second-guessed myself so many times before finally hitting the the "easy button" and just going by your list. Thanks.

 

[badtlc]

Molakule, there is nothing confusing about your list. But your list wasn't the discussion. I think greg's answer was the closest to describing what I couldn't figure out. If synchromesh is most often the term used because it meets GM's specification for synchromesh, then that makes a lot of sense. It also sounds like as a rule if a fluid is listed for use in synchronized transmissions, then it has to have a GL-4 level add pack along with friction modifiers. Therefore, the GL-4 is implied by saying the fluid is applicable for synchronized transmissions. This is what I wanted to know. I wanted to know how to tell by looking at any fluid (especially ones not on molakule's list) specifically synchromesh fluids and tell if they provide a GL-4 level of protection even though they don't advertise that. Thanks for everyone's help.

 

[MolaKule]

It does get confusing at times and the companies producing these products don't necessarily help the issue. If you see an MTL that you think should be added to this unofficial list, let us know. We'll investigate it and see if it qualifies for a GL-4 and/or GL-5 synchromesh fluid.

 

[badtlc]

Originally Posted By: MolaKule

It does get confusing at times and the companies producing these products don't necessarily help the issue. If you see an MTL that you think should be added to this unofficial list, let us know. We'll investigate it and see if it qualifies for a GL-4 and/or GL-5 synchromesh fluid.

This raises another question... Can a synchromesh type fluid provide GL-5 application protection? If so, do you know of any?