GL 4 Gear Oil Requirement

[GCecchetto]

Amazingly, not much comes up when you search for "gear oil" relative to what is required for the Meritor axles. My understanding is that GL4 gear oil is specified and I'm curious if that is because of GL4 being safe for yellow metals? Reading through a Meritor maintenance document, they recommend GL5 gear oil. I realize that document is basically referring to their axles used in over the road trucks that don't have features like CTIS, so maybe there are yellow metals used in the axles on these trucks that aren't used in their other axles.

Anyway, I would like to switch to a full synthetic in the diffs and hubs and there are many more GL5 options and GL5 is rated for higher loads than GL4. Was wanting to use Mobil 1 Delvac 1, but it says "not recommended for use in applications requiring GL4", so I guess that is out. Just curious why the GL4 requirement. Thanks

 

[GeneralDisorder]

There is really no compelling reason to use synthetic in the axles. It's just a waste of money. There's no combustion products to contend with and the temps are not high and are actually significantly lower with the ECO hubs making it an even less demanding application. The military doesn't use synthetic and the axles are one of the most reliable components even in military use. The question you have to ask is what are you getting for your money? I'm an Amsoil dealer and I don't put synthetic in the axles. Don't drink that cool aid.

I would use what the TM calls for. A brand name GL4 - although the military buys from whoever will supply the stuff at the spec and the best price.

*edit* - I should clarify that the Army doesn't use synthetic *gear oil* in trucks. They may have other uses for it and they DO have synthetic 15w40 and Dexron ATF in the system for trucks. Just not gear oil that I have encountered.

 

[GCecchetto]

There is really no compelling reason to use synthetic in the axles. It's just a waste of money. There's no combustion products to contend with and the temps are not high and are actually significantly lower with the ECO hubs making it an even less demanding application. The military doesn't use synthetic and the axles are one of the most reliable components even in military use. The question you have to ask is what are you getting for your money? I'm an Amsoil dealer and I don't put synthetic in the axles. Don't drink that cool aid.

I would use what the TM calls for. A brand name GL4 - although the military buys from whoever will supply the stuff at the spec and the best price.

*edit* - I should clarify that the Army doesn't use synthetic *gear oil* in trucks. They may have other uses for it and they DO have synthetic 15w40 and Dexron ATF in the system for trucks. Just not gear oil that I have encountered.

Curious which GL4 oil you are using?

 

[glcaines]

I use GL-4 in the axles of all of my MVs. I use NAPA brand, which I understand is Valvoline for a lot less money.

 

[GCecchetto]

Okay, so I've spent more time than I care to admit trying to find a GL4 gear oils. Most of the oils, like Valvoline say GL% and can also be used in GL4 applications. However, from what I have learned from talking with the tech folks at several major oil companies, is that a gear oil cannot be GL% rated and be safe for yellow metals. So, when it say also meets GL4 but you ask the tech guys if it's safe for yellow metals they say no. So far, the only GL4 oil I have found that states it's yellow metal safe is Penngrade 1.

I looked through Valvoline's offerings and didn't find a specific GL4 oil, they all said meets GL5 and GL4. I understand that the only place there is yellow metal in our axles is the front hubs, so in theory, GL5 should be preferred in the diffs and a GL4 in the hubs. Ultra1Plus does make both a conventional and synthetic GL4 gear oil, but there is very little info available and what is available does not mention yellow metals. I will email them and see what they say, although I would rather use a name brand. Not trying to belabor this, but I think many folks are running oils they think are okay, but actually aren't, in the hubs anyway. I'm sure I'm missing some oil, so please point me in the right direction.

 

[GeneralDisorder]

Not sure exactly where the yellow metal is to be found in the front hubs but regardless the whole "yellow metal safe" discussion is largely irrelevant as nearly all modern GL4/GL5 dual-spec lubricants are safe in that way. Amsoil for example:

https://www.amsoil.com/t/faq/

Scroll down to Gear Oils and click on "Are AMSOIL gear lubes safe for yellow metals?"

I just run whichever supplier (NAPA, Autozone, etc - they all deliver to my shop) can give me the best price on a 5 gallon pail of 80w90. Positive it's a GL5.

Personally I would rather have twice the Extreme Pressure additives of GL5 than not be slightly corrosive (at very high temperature I'll never reach in the presence of moisture that won't accumulate due to regular driving) to yellow metals.

If you want what the military uses - well it's a GL5

 

[MrMikey4026]

Not sure exactly where the yellow metal is to be found in the front hubs but regardless the whole "yellow metal safe" discussion is largely irrelevant as nearly all modern GL4/GL5 dual-spec lubricants are safe in that way. Amsoil for example:

https://www.amsoil.com/t/faq/

Scroll down to Gear Oils and click on "Are AMSOIL gear lubes safe for yellow metals?"

If you want what the military uses - well it's a GL5

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View attachment 910079

Not in the hubs, the axle busing inside the front spindles.

 

[GeneralDisorder]

Not in the hubs, the axle busing inside the front spindles.

I kinda figured those might be looking at the exploded diagram. Still irrelevant but yeah that's what I was thinking - not in the hubs but in the spindles.

 

[GCecchetto]

Not in the hubs, the axle busing inside the front spindles.

But the oil that would be in contact with the spindle bushings is the oil in the hub, correct?

 

[GCecchetto]

Not sure exactly where the yellow metal is to be found in the front hubs but regardless the whole "yellow metal safe" discussion is largely irrelevant as nearly all modern GL4/GL5 dual-spec lubricants are safe in that way. Amsoil for example:

https://www.amsoil.com/t/faq/

Scroll down to Gear Oils and click on "Are AMSOIL gear lubes safe for yellow metals?"

I just run whichever supplier (NAPA, Autozone, etc - they all deliver to my shop) can give me the best price on a 5 gallon pail of 80w90. Positive it's a GL5.

Personally I would rather have twice the Extreme Pressure additives of GL5 than not be slightly corrosive (at very high temperature I'll never reach in the presence of moisture that won't accumulate due to regular driving) to yellow metals.

If you want what the military uses - well it's a GL5

View attachment 910078

View attachment 910079

This is exactly why I was asking the question. I would much prefer the benefits of a GL5 oil. If the yellow metal issue with GL5 oils is only at high temps, then this a complete no issue, even my rear hubs, that are a pretty good indication of the diff temp since they share the same oil are only slightly warm to the touch after many hours a freeway cruising at 60+ MPH. Front hubs even cooler. Haven't checked the front diff temp, but I doubt it's any warmer than the rear. Likely cooler since it's only getting 30% drive when the center diff isn't locked.

 

[MrMikey4026]

But the oil that would be in contact with the spindle bushings is the oil in the hub, correct?

Yes

 

[GCecchetto]

Just got off the phone with tech support at Mobil 1 and asked them if Delvac 1 was safe for Yellow metals. The answer was no. I then asked, what if the operating temp was below 250 degrees, then the answer was yes, it's safe for yellow metals. Case closed for me. When I redid the install of the one front eco hub that was leaking badly, I filled the hub with Delvac 1 75W-90. Was getting ready to change the oil before proceeding with the rest of the hubs. Leaving the Delvac 1 in and will be using it in the other front hub at a minimum, possibly front and rear axles too.

 

[glcaines]

Most of my MVs have been manual transmission, and you don't want to use GL-5 with yellow metal. It is much easier to stick with GL-4 on everything I have, and it is readily available. All you need is GL-4 spec compatible. Actually, the API has discontinued the spec for GL-4, but there are plenty of sources of lube that meet the old GL-4 spec. GL-5 is not backwards compatible with GL-4. If you have a need that specifies GL-4 you should use GL-4. If you have a vehicle specifying GL-5, you should definitely use GL-5.