GL-5 in place of GL-4

[moribundman]

Originally Posted By: Audi Junkie
I know guys I trust who have used M1 gear oil in Audi manual trans and they say it's fine. It calls for GL-4.


That's why one of us at the 12v forum called Mobil to settle the issue. That's when the Mobil CS person said the corrosion issue with yellow metal occurred only at temperatures normally not seen in a manual transmission of a street-driven car. The Mobil guy did however not go as far as to recommend using the Mobil GL-5 lube.

Yes, people have used the Mobile GL-5 lube without issues. I think everybody will have to make the decision to take a risk, as small as it may be, all by himself. I certainly wouldn't want to talk anybody to go against the recommended spec, even, it it is, as Mola said, an "obsolete" spec.

The rear differential in my quattro calls for GL-5 lube, by the way.

 

[moribundman]

Originally Posted By: MolaKule
My position is: For synchromesh transmissions, I would use a manual-transmisson-specific gearlube rated for GL-4 protection in which the D-140 rating was preferably 1A.

For a heavy duty truck or semi transmission, I would use a
GL-5/MT-1 rated lube and let er rip.


Well, that's all cherry, but why did you say GL-4 was obsolete?

Originally Posted By: MolaKule
Indeed GL4 is an obsolete specification.

 

[G-MAN]

Originally Posted By: moribundman
Originally Posted By: MolaKule
My position is: For synchromesh transmissions, I would use a manual-transmisson-specific gearlube rated for GL-4 protection in which the D-140 rating was preferably 1A.

For a heavy duty truck or semi transmission, I would use a
GL-5/MT-1 rated lube and let er rip.


Well, that's all cherry, but why did you say GL-4 was obsolete?

Originally Posted By: MolaKule
Indeed GL4 is an obsolete specification.



GL-4 "gear lube" is obsolete. But a manual transmission specific gear lube that meets GL-4 protection requirements is not. Most any synchromesh fluid meets GL-4.

 

[moribundman]

Well, it wasn't stated clearly.

 

[Audi Junkie]

My opinion is to use an easily availible inexpensive GL-5 like Mobil 1 in the diffs and find a specific GL-4 you like and are comfortable with for the trans, if "required".

 

[moribundman]

Sounds fine by me.

 

[MolaKule]

Quote:
Well, that's all cherry, but why did you say GL-4 was obsolete?


What G-MAN stated is right on.

Quote:
GL-4 "gear lube" is obsolete. But a manual transmission specific gear lube that meets GL-4 protection requirements is not. Most any synchromesh fluid meets GL-4.


While the GL-4 specification is obsolete , the synchromesh manual transmission lubes are formulated to the GL-4 protection level in terms of EP additives, with the addition of specific friction modifiers for proper synchro engagement. Since the gearing and bearings in a synchromesh transmission are not as highly loaded as in a hypoid-design differential, the EP additive level is necessarily lower. Just because a GL-4 specification is obsolete, that doesn't mean we cannot use the protection rating for specialty applications such as synchromesh transmissions.

The GL-5 rated differential lubricants do NOT have the specialized friction modifiers built into them. Yes, they have friction modifiers, but these are very different friction modifier compounds for the benefit of limited slip mechanisms, and contain about twice the EP additives (as compared to GL-4 rated synchromesh lubes) for the highly loaded hypoid, highly offset pinion drives.

The dual rating of GL5/MT-1 means a fluid can be used in differentials as well as heavy duty truck transmissions, but I do NOT recommend these fluids for passenger car and light truck synchromesh Manual Transmissions. Different fluid, different application.

 

[MolaKule]

Quote:
That's why one of us at the 12v forum called Mobil to settle the issue. That's when the Mobil CS person said the corrosion issue with yellow metal occurred only at temperatures normally not seen in a manual transmission of a street-driven car. The Mobil guy did however not go as far as to recommend using the Mobil GL-5 lube.


You will notice that Mobil does not have a synchromesh fluid on the market.

I find that many people, even those that are in large oil companies, are very uninformed about synchromesh fluids per se. One reason I suppose is that they have their standard differential, hydraulic, and engine lubes for the general market and that's where their emphasis lay, whereas synchromesh fluids are specialty fluids.

The exception might be Pennzoil and Texaco since they do have synchromesh fluids.

BG Synchroshift is another, albeit a rather costly fluid.

 

[Audi Junkie]

Let's get into some Dual-Rated fluids discussion, lol.

fwiw, GM Syncromesh is very popular in the Acuras to avert the 6th gear crunch. It's very light.

 

[zoomzoom]

hm this is very interesting topic!

I have Audi S4 and I am currently running motul gear 300 oil in both transmission and rear diff.

Here is how the its specs compare to OEM fluid:

Motul Gear 300:
Viscosity grade SAE J306 75W-90
Density at 15°C (59°F) ASTM D1298 0.900
Viscosity at 40°C (104°F) ASTM D445 72.6 mm²/s
Viscosity at 100°C (212°F) ASTM D445 15.2 mm²/s
Viscosity index VIE ASTM D2270 222
Flash point ASTM D92 200°C / 392°F
Pour point ASTM D97 -60°C / -76°F


OEM:
SAE 75w90
API GL-4/5
VW 501.50

Density at 15?C (59?F) 0.864
Viscosity at 40?C (104?F) 76.0
Viscosity at 100?C (212?F) 14.0
Viscosity index VIE 200
Flash point 224C
Pour point -51C


What do you guys this is motul good substitute?

 

[gpshumway]

Originally Posted By: Al

I wonder why it is that Subaru recommends GL-5 for their manual transmission and Nissan recommends GL-4. Presumably both transmissions are very similar design/composition and presumably both companies are capable of recommending the correct lube for their transmissions.


Except they are probably not similar in design/composition. I don't know which Nissan transmission you're referring to, but Subarus have longitudinal engines, and their transmissions have hypoid gears in them which require the extra EP additives of a GL-5. Nissan FWD cars have transverse engines and don't have hypoid gears in the transmission, and Nissan AWD cars (G35x) have a separate transfer case, I believe.

 

[Audi Junkie]

I don't think specs are the whole story in a trans app and certianly not in a diff. I say use Mobil 1 in the diffs and fugget aboud it. In the trans, experimentation is a good approach.

 

[moribundman]

Originally Posted By: MolaKule
Quote:
Well, that's all cherry, but why did you say GL-4 was obsolete?


What G-MAN stated is right on.

Quote:
GL-4 "gear lube" is obsolete. But a manual transmission specific gear lube that meets GL-4 protection requirements is not. Most any synchromesh fluid meets GL-4.


While the GL-4 specification is obsolete , the synchromesh manual transmission lubes are formulated to the GL-4 protection level in terms of EP additives, with the addition of specific friction modifiers for proper synchro engagement. Since the gearing and bearings in a synchromesh transmission are not as highly loaded as in a hypoid-design differential, the EP additive level is necessarily lower. Just because a GL-4 specification is obsolete, that doesn't mean we cannot use the protection rating for specialty applications such as synchromesh transmissions.


What are some of the current and not obsolete MT lube ratings? Especially I would like to know for what rating current VW, Audi, and Porsche cars call. Also, do I rightly presume those current lubricants are backwards compatible with obsolete MTs calling for GL-4?

 

[Audi Junkie]

There are now specific VW specs for MTF. Not long ago, it was just generic MT specs....but there is no revenue stream in that.

 

[MolaKule]

Quote:
What are some of the current and not obsolete MT lube ratings? Especially I would like to know for what rating current VW, Audi, and Porsche cars call. Also, do I rightly presume those current lubricants are backwards compatible with obsolete MTs calling for GL-4?


https://bobistheoilguy.com/forums/threads/gear-tribology-and-lubrication-part-i.57856/

See post 729255.

I would NOT assume this but consider them on a case-by-case basis.

 

[moribundman]

Originally Posted By: Audi Junkie
There are now specific VW specs for MTF. Not long ago, it was just generic MT specs....but there is no revenue stream in that.


My '96 requires SAE 75W-90 GL-4 in the MT (and in the torsen differential) and SAE 90 GL5 in the rear differential.

I will contact Audi and find out the exact current spec and generic equivalent. If GL-4 is indeed obsolete, some other spec must have take its place. I will ask them about that also.

 

[G-MAN]

Originally Posted By: moribundman
Originally Posted By: Audi Junkie
There are now specific VW specs for MTF. Not long ago, it was just generic MT specs....but there is no revenue stream in that.


My '96 requires SAE 75W-90 GL-4 in the MT

 

[byez]

Every application is different.

In the RX8 world, GL5 or GL4 was recommended for the manual transmission in early models as stated in the manual.

The GL5 was believed to be the cause of transmission failure and in later models only GL4 was recommended.

 

[byez]

Happily running Redline GL-4 MTL in my transmission.

I was previously running Esso GL-5 75w90 gear oil and found it more notchy and harder to get into gear. Whether it was switching from a dino to a synthetic or GL-5 to GL-4 I am not sure but I will continue to use GL-4.

 

[aquariuscsm]

Originally Posted By: G-MAN
Originally Posted By: moribundman
Originally Posted By: Audi Junkie
There are now specific VW specs for MTF. Not long ago, it was just generic MT specs....but there is no revenue stream in that.


My '96 requires SAE 75W-90 GL-4 in the MT

^^THEE best!!!!!!! I`ve tried several different gear oils in my manual transmission and Amsoil MTG is the best stuff on the planet! Their rear differential GL5s are awesome as well! That`s all I`ll ever use.