GL-4 vs GL-5

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Al

Al

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A long ago we had a discussion about these specs. In theory most Transmissions call for GL-4 because theoretically the synchronizers can not tolerate the GL-5. At the time this was discussed we had a former rep (I believe-from Mobil) post a differing opinion:

He indicated that the GL-4 was no longer a valed spec. He also indicated that the additives in GL-5 have been upgraded to the extent that it is fine for brass synchros.

Any updates here ???
 
I was recently looking at tranny fluids and gear oils, because I want to change both fluids. My '96 A4 Quattro calls for G4 spec tranny fluid and GL5 rear differential oil. GL5 spec lube will attack brass synchros due to high sulfur content.

Now, I've seen there is a bunch of GL4 fluids that pass GL5 requirements, while also meeting GL4 specs. Those fluids should be okay to use in applications that require GL4.
 
Moribundman,

"GL5 spec lube will attack brass synchros due to high sulfur content." is not exactly correct.

In the past, the additives in the gear oil that allowed it to pass the GL-5 test did indeed corrode yellow metals, brass, bronze, etc. Many modern GL-5 gear oils have a different additive package that is not corrosive to these yellow metals...but the user needs to check the data sheet to find out this information.


Ken
 
Most of the newer (US) formulations of Sulfur/Phos EP are buffered and are not too bad on bonze and soft metals. But they will still adhere too well and prevent synchronization of some transmissions. I have a Toyota synchronizer on my desk that is agresive enough to break through the EP and synchronize, but I've see a lot that can't break through that chemical bond.
The only "safe" GL-5's that I know of for GL-4 application are those with Borate EP additives like Delo Gear, which I use sucessfully in a lot of GL-4 applications, including the ZF truck transmissions that burn up with GL-5 sulfur/phos. Although Chevron developed the Borate EP technology, I think there are a couple of other brands in the US that produce products with it.
 
Well, Ken, what you say may be true, but I was speaking in terms what's in my tranny and rear differential. The stuff in the rear stinks NASTY definitley sulfur, and my manual tells me NOT to use a GL5-rated fluid in the tranny.
 
/\ /\
Augh, for once I wish I wouldn't make some typos.
shocked.gif


So, Ken, how can I find out what are the best tranny fluid and rear differential oils are for my Audi?

I need a GL4 SAE 75W-90 tranny fluid and GL5 SAE 90 rear differential oil. Would Redline MT-90 (synthetic 75W90) and Redline 75w90 GL5 oil work?
 
recently i called mobil about using their mobil1 gl-5 in a gearbox that spec'd gl-4 because of bronze gears. i figured with it being synthetic maybe it didn't contain the same additives that conventional oil does. he looked in his books and talked to the other reps then came back on and told me "i wouldn't use it in there". i now run mobil SHC in those gear boxes which is designed to run with bronze gears and is much cheaper. the only problem is that i had to buy a 5 gallon pail and i can refil all of the gear boxes with 1 gallon
freak2.gif
 
I wish I had time to post all the information on gl4 vers gl5 as many are concerned with copper corrosion in gl5. This is not correct. Gl-5 actually has higher requirements against copper corrosion than the gl-4.

code:
gl-4 gl-5



Copper Corrosion ASTM D 130: ASTM D 130:

3b max after 3max after

1h at 121.1degC. 3h at 121.1degC


Click to expand...
Here is the basic about the difference in gl-4 vers gl-5

API GL-4
Denotes Lubricants intended for axles with spiral bevel gears operating under moderate to sever conditions of speed and load or axles with hypoid gears operating under moderate speeds and loads. These oils MAY be used in selected manual transmissions and trans-axle applications where API MT-1 lubricants are unsuitable.

API GL-5

Denotes lubricants intended for gears, particularly hypoid gears, in axles operating under various combinations of high speed shock loads and low speed, high torque conditions. Lubricants qualified under MIL-L-2105D satisfy the requirements of the API GL-5 specifications.

API MT-1

Denotes lubricants intended for non synchronized manual transmissions used in buses and heavy duty trucks. Lubricants meeting the requirements of API MT-1 provide protection against the combination of thermal degradation, component wear and oil seal deterioration. API MT-1 does not address the performance requirements of synchronized transmissions and trans-axles in passenger car and heavy duty applications.

Discontinued Api not in current use.

API GL-2
API GL-3
API GL-6


Anyway, this is just a touch of what the difference is between some of the classifications. The big difference is EP additives and the type of gears they are designed for. BOTH GL-4 and GL-5 address the copper issue and Both are compatible in this area.

There's more to this on specs and such but as I was researching this, I kept looking at the schaeffers 267 gear oil tech data and noticed that they show to cover the MT-1 specs, the SAE J2360 spec, the MIL 2105 spec all of which makes a better oil than standard gl-4. As pointed out above, its the design for specific load and gear types that make it different and that's based on the fact there is a difference in ep additives between the two.

I hope this helps clear up the mis information about corrosion to copper and such.
 
quote:
Originally posted by Pablo:
GREAT post Bob. I almost have quit explaining that modern GL-4 and/or Gl-5 will NOT eat yellow metal (Cu, brass, bronze) - that is a strong myth.
Click to expand...
I know, it does get somewhat fustrating but that's what we're here for, to help explain as most of this info gets started by someone that has no real clue. I can understand that as there just isn't enough info available to help educate about these things.
 
quote:
Originally posted by Pablo:
GREAT post Bob. I almost have quit explaining that modern GL-4 and/or Gl-5 will NOT eat yellow metal (Cu, brass, bronze) - that is a strong myth.
Click to expand...
Yes-great post Bob. Yet still there are Mobil 1's words basically saying their oil is unsat for trans requiring GL-4. Looks like a matter of product liability concerns. Thats typical for Mobil 1.
mad.gif
 
Until now, everyone who knows the requirements of Audi trannsmissions has told me NOT to use any GL5-rated fluid, because those WILL ruin the brass synchros (Someone told me he installed steel synchros, so for him it didn't matter. So, is a GL5-rated fluid okay, if it's also rated GL4? As I said, I would think so. It seems some GL4-rated products also exceed GL5 specs (Redline/Neo). I just don't feel like buying the VW/Audi fluids, which cost over 20 bucks a quart!
 
quote:
Originally posted by Al:

quote:
Originally posted by Pablo:
GREAT post Bob. I almost have quit explaining that modern GL-4 and/or Gl-5 will NOT eat yellow metal (Cu, brass, bronze) - that is a strong myth.
Click to expand...
Yes-great post Bob. Yet still there are Mobil 1's words basically saying their oil is unsat for trans requiring GL-4. Looks like a matter of product liability concerns. Thats typical for Mobil 1.
mad.gif

Click to expand...
Well, again, tech support really didn't have a real clue if he left em hanging to confer with others about this issue so I'd agree with the liability concern so error on the side of caution. If they'd looked up their tests info on their gear oils, and if they meet the gl-5 ratings as well the mt-1 and ASTM d 130, along with the mil spec 2105d for channeling and such, there'd really be no question on this. Where the friction modifiers are a big concern in certain things are where clutches are in play such as a wet clutch. Then would you want to consider a lower frictional/antiwear gl-4 based oil but as for the bronze,copper corrosion concerns, all of these oils are tested for that as that is not acceptable to show corrosion.

a gl-4 doesn't even have to test out for thermal and oxidation stability/component cleanliness- l-60-1 test where a gl-5 and api mt-1 does.

Theres even a test for corrsioin resistance in the presence of water. The L-33 test must show no reusting after 7days exposure on any working surface which is the l-13 or l-21 test.

Basicly, as long as the gear lube meets and exceeds the following specifications and manufacturer’s requirements: API Service Classification GL-5, MT-1, Military Specification MIL-PRF-2105E, and SAE J2360, then you should have no problem running it in place of a gl-4.

[ July 04, 2003, 02:53 PM: Message edited by: BOBISTHEOILGUY ]
 
quote:
Originally posted by moribundman:
Until now, everyone who knows the requirements of Audi trannsmissions has told me NOT to use any GL5-rated fluid, because those WILL ruin the brass synchros (Someone told me he installed steel synchros, so for him it didn't matter. So, is a GL5-rated fluid okay, if it's also rated GL4? As I said, I would think so. It seems some GL4-rated products also exceed GL5 specs (Redline/Neo). I just don't feel like buying the VW/Audi fluids, which cost over 20 bucks a quart!
Click to expand...
A GL-4 cannot be rated as a GL-5 also. A GL-4 has lower ep additives and to meet the GL-5 specs, then they'd have to increase that, which then it would be higher in those additives than a GL-4. Also, a GL-4 doesn't have to be tested for thermal oxidation stability, channeling characteristics where the gl-5 does.
 
Forgive Bob if I missed it. Which Shaeffer's products would satisfy the specs: GL-5, MT-1, Military Specification MIL-PRF-2105E, and SAE J2360
 
Last time I picked up a pail of gear lube it was rated GL4/GL5. I guess I am luck that I own mostly Toyota's! They let you use GL4 or GL5 in their transmissions so long as viscosity is right!
 
if gl-5 basically exceeds gl-4 as you claim then why do some oems specify gl-4 for certain applications? the 3 different manufactures of worm drive gear reduction units i have (all the same basic design) they all specify mobil SHC 460 which i was told by the local oil guy specs to a gl-4. the previous facility guy filled them with mobil1 (gl-5). one of them failed, the bronze gear completely wore out, and while repairing it is when i found the spec for mobil SHC 460.
i am not doubting you that they are interchangeable i just find it interesting that gl-5 has not replaced gl-4 or that any lubes claim to be gl-4/gl-5.

[ July 04, 2003, 11:49 PM: Message edited by: tom slick ]
 
I've been warned by other Audi drivers not to put any GL5 tranny fluid in my Quattro. They say it WILL ruin the synchros. Audi demands GL4 for the tranny and the torsen, and GL5 for the rear differential. I guess, I'll just go with the overpriced OEM Audi fluids, because I'm not going to find a concrete answer.
 
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