Multiple specifications in gear oil question

[Planb]

How can a gear oil be formulated to achieve gl-3, gl-4 and gl-5 in a single bottle?

My understanding is that the high pressure additives are increased over each other.

 

[Rand]

gl-3 is obsolete?

dual rated oils I'm guessing its one of those "meets or exceeds" type thing.

Personally I dont use dual rated gear oils. If its dual rated its basically gl-5

 

[DeepFriar]

I tend to agree about the multi-flavor GL-5s and I don't use them either. Interestingly though RP goes out of their way to say that their MaxGear product will not harm any of the yellow metals which is what most of us GL-4 guys worry about. So maybe whatever EP they are using is "safe". Don't know.

 

[MolaKule]

http://www.bobistheoilguy.com/forums/ubb...tion#Post729255


http://www.bobistheoilguy.com/forums/ubb...tion#Post729289

 

[DeepFriar]

Key words in that thread? - "Metal deactivators"

Requires a degree of trust then if you use multi-GL instead of GL-4 where GL-4 is specced. With RP, for instance, having gone out of their way as I said earlier, to state that theirs is safe for GL-4, I would tend to "trust" them. I might be less inclined to trust many others.

 

[MolaKule]

Originally Posted By: DeepFriar
Key words in that thread? - "Metal deactivators"

Requires a degree of trust then if you use multi-GL instead of GL-4 where GL-4 is specced. With RP, for instance, having gone out of their way as I said earlier, to state that theirs is safe for GL-4, I would tend to "trust" them. I might be less inclined to trust many others.


I don't know why one would trust RP over any other Manf. who makes the same claims.

I think we have to look at the targeted application.

What fluid type and protection level do most manual light truck and car transmissions and transaxles require?

It is a a dedicated MTF with a GL-4 level of protection that can be accomplished by using a medium level of AW additives consisting of ZDDP and other boosters with a specialized friction modifier.

What level of protection do the majority of modern differentials require? It is a GL-5 level of protection.

This is accomplished by using an EP additive package consisting of S-P and boronated additives.

It is a fact that today's EP chemistries are 'buffered" using metal inhibitors and anti-corrosive additives. What this means is that yellow metals such as copper (brass/bronze) alloys don't get attacked.

When was the last time you saw any modern hypoid differential that contained anything but steel components?

But the GL-5 lube could also be used in worm drive automotive and industrial gearboxes containing copper (brass/bronze) alloys because of the chemistry described above, even if the gearbox's protection requirement was GL-1, GL-2, GL-3, or GL-4.

So the answer "yes," it can be and is formulated for that range of protection levels.

Quote:
The GL-X rating defines the protection level for gearing, whether it be transmissions, TC's, or differentials.

A GL-5 rating is for highly-loaded gears (high tooth contact forces), such as for hypoid differentials, and contains high levels of primary and secondary Extreme Pressure (EP) additives such as Sulfur-Phosphorus chemistry. The viscosity of said GL-5 gear lubes is usually higher than for manual transmission lubes. For example, a 75W90 GL-5 gear lube has a viscosity of 18.5 cSt@100C, whereas a GL-4 protection rated 75W90 Manual Transmission lubricant would have a viscosity of 14.0 cSt@100C. This difference in viscosity can have a major impact for Manual Transmission shifting performance in terms of cold weather shifter fork movement.

A GL-4 rating is for lower loaded gearing such as for manual transmissions (MT) and Transfer cases (TCs) in light trucks and cars. It contains mostly an Anti-Wear additive (AW) in the form of ZDDP or an equivalent anti-wear package. It does not contain Extreme Pressure (EP) additives. Furthermore, the chemistry for MT's contain specialized friction modifiers for the synchronizer assemblies.

The GL-4 Performance Improvement package (additive package) has been tested by the additive suppliers to perform to GL-4 protection levels using modern testing machines.

For manual transmissions that share the same sump with hypoid differentials, such as the Subaru drivelines, a special GL-5 lubricant is used which has the synchromesh friction modifier. But this is an exception.


http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/1231182/3

 

[Planb]

When was the last time you saw any modern hypoid differential that contained anything but steel components?

What about something like a Subaru, the gearbox and differential are in the same bath.

Thank you for posting the links, your work is much appreciated.

 

[MolaKule]

Quote:
For manual transmissions that share the same sump with hypoid differentials, such as the Subaru drivelines, a special GL-5 lubricant is used which has the synchromesh friction modifier. But this is an exception.

 

[Planb]

So if gl-5 is anti corrosive, has a superior EP package, why list that it works in a gl-3, gl-4 application?

I mean SN works in a SM application.

 

[DeepFriar]

Don't get me wrong, I am just as cynical as your average guy relative to corporate promises. What I have seen though is that many, many suppliers of the supposed multi-GL products do not make any further statement as to yellow metals or anythng else. I was simply pointing out that RP did at least make the statement. And unlike a lot of other lower tier suppliers RP has a lot to lose in terms of brand hence the "trust" such as it is.

 

[DeepFriar]

Just to close the loop on the above... I'm not defending RP nor do I use their Max Gear. I stick with straight GL-4 RL MT-90 in the Nissan transaxle.

 

[DWC28]

Excuse me if this is all covered or just skip. A possible another way of looking at the subject. Lubricant additives can be broken into many categories. One beneficial way is surface active versus non surface active. Additives such as AW, EP, corrosion inhibitors, detergents, FM, rust inhibitors and etc. are surface active. This means they compete against each other for “metal” surface on which to work. The additive balance must be correct for each to work correctly. Some GL-4 tests are no longer available so no new additives cannot be completely tested. Companies that claim both GF-4 and 5 are assuming that they can now pass GL-4 at the Gl-5 treat rate since the EP additive portion is not as active as older EP varieties.

 

[MolaKule]

Quote:
...Some GL-4 tests are no longer available so no new additives cannot be completely tested...


Additive formulations can be tested and are tested by the additive makers using FZG and other testing machines to the GL-4 protection rating.

 

[MolaKule]

Originally Posted By: Planb
So if gl-5 is anti corrosive, has a superior EP package, why list that it works in a gl-3, gl-4 application?

I mean SN works in a SM application.


If it covers prior protection ratings, why not?

 

[Planb]

Originally Posted By: MolaKule
Quote:
For manual transmissions that share the same sump with hypoid differentials, such as the Subaru drivelines, a special GL-5 lubricant is used which has the synchromesh friction modifier. But this is an exception.


Does the friction modifier increase or decrease friction?

In a differential I assume it decreases friction to allow the plates to slip, preventing chatter.

 

[MolaKule]

Quote:
Does the friction modifier increase or decrease friction?



If you are referring to the Subaru GL-5 synchromesh, it contains specific friction modifiers for the synchros.

Quote:
In a differential I assume it decreases friction to allow the plates to slip, preventing chatter.


In a Limited Slip Differential, there is a specific specific friction modifier chemistry to inhibit chatter, which is dynamic or "stick-slip" friction.