Add pack to meet GL-4

[supercity]

Hi

GL-4 gear oils seem to use either Zinc or "sulfur-phosphorous" as the main AW/EP additive. Is there any significant performance difference between these 2 add packs when used in a manual transmission that does not contain hypoid gears? i.e. typical FWD, RWD and some AWD transmissions.

I understand Zinc formulations are less corrosive to yellow metal but most S/P formulations are said to use non-active S/P anyway. I've noticed Zinc seems to be favored in "non EP" commercial applications (Road Ranger etc) and most of these lubes seem to meet GL-4 performance also.

 

[Whitewolf]

A common approach to satisfy GL-4 requirement has for some time been to simply use a GL-5 additive treated at 50%. Thus the additive chemistry would be exactly the same. For manual transmissions the trend is to replace GL-4 fluids with specialized manual transmission fluids designed specifically for that purpose.

 

[MolaKule]

Originally Posted By: supercity
Hi

GL-4 gear oils seem to use either Zinc or "sulfur-phosphorous" as the main AW/EP additive. Is there any significant performance difference between these 2 add packs when used in a manual transmission that does not contain hypoid gears? i.e. typical FWD, RWD and some AWD transmissions.

I understand Zinc formulations are less corrosive to yellow metal but most S/P formulations are said to use non-active S/P anyway. I've noticed Zinc seems to be favored in "non EP" commercial applications (Road Ranger etc) and most of these lubes seem to meet GL-4 performance also.



There are many threads here addressing your question

http://www.bobistheoilguy.com/forums/ubb...sio#Post1231182 but,

Hypoid (diffrential) Gear lubes can be rated GL-5 f they have primary and secondary Extreme Pressure additives to assist the drive pinion and ring gears when the mating teeth transfer torque and slide and roll on each other.

A hypoid differential lubricant has Extreme Pressure additives and also contains heavier cuts or viscosities of base oils to provide thicker films for the increased loading.

Dedicated MTL's have the correct viscosity, anti-wear package, and friction modification needed for MT's.

 

[MolaKule]

I.E.,

There are three important characteristics a dedicated MTL must have:

1. the correct viscosity,

2. the proper anti-wear package and,

3. the correct friction modification needed for MT's.

 

[supercity]

Thank you for the reply. I can't help but think my question went misunderstood though.

I was trying to understand the main difference in AW/EP chemistry between different GL-4 manual transmission specific fluids, not how they differ to hypoid GL-5 lubes. I understand the the overall formulation is carefully balanced but can predominantly use either Zinc or S/P as the main EP/AW additive.

I was wondering if there was a preference for one or the other and if there are any performance differences.

 

[MolaKule]

Historically, and in the days when three- and four-speed manual transmissions were the norm, formulators used (as Whitewolf stated) about a 50% treatment of an S-P EP additive, the same as used in differentials.

Today, many additive packs use about 2000ppm of ZDDP which is an anti-wear additive. With the type of gears used and their tooth profile's, the loading on the gear teeth doesn't need an EP additive.

In addition, the move to new ashless organic formulas have allowed formulators to use less S-P-Z organo-metallic additives. This allows us to use lower levels of metal inhibitors and acid scavengers, which results in longer drain intervals.

Today, the emphasis is on shiftability and engagement for the synchro assembly using new friction modifier chemistry's.

With the trend toward thinner and thinner fluids for fleet CAFE numbers, and with the move toward higher HP engines, I welcome the new low-ash formulas.

I hope this helps.

 

[supercity]

More info to file away..Thanks Mola

 

[d00df00d]

Thanks, Mola!

What is it about metal inhibitors and acid scavengers that limit drain intervals?

 

[MolaKule]

Originally Posted By: d00df00d
Thanks, Mola!

What is it about metal inhibitors and acid scavengers that limit drain intervals?


Good question and I should clarify.

Quote:
In addition, the move to new ashless organic formulas have allowed formulators to use less S-P-Z organo-metallic additives. This allows us to use lower levels of metal inhibitors and acid scavengers, which results in longer drain intervals.


It's not so much that metal inhibitors and acid scavengers are bad, but they are sacrificial chemistries with a specific lifetime.

When they do degrade, they no longer do their job and wind up thickening the lube as they, themselves, oxidize.

So by having less acid buildup, one can use lower treatment levels of metal inhibitors and acid scavengers, and the fluid can maintain its target viscosity over a longer period.

 

[MolaKule]

BTW, we should emphasize again that the GL-4 rating for gear lubes is primarily a gear and bearing protection rating for systems that are not as heavily loaded as those found in hypoid differentials or Heavy Duty truck transmissions.

It should NOT be assumed than ANY gear lube with the GL-4 rating is suitable for Manual Transmissons.

Dedicated or application specific MTL's not only have the necessary Anti-Wear chemistry to attain a GL-4 rating, but also have the correct viscosity and friction modification for synchronized transmissions.

Bottom line is, there is more to a Dedicated or application specific MTL than just a GL-4 rating.

 

[d00df00d]

Got it. And what is the function of the S-P-Z organo-metallic additives you cited, and of the ashless organic formulas that are displacing them?

 

[MolaKule]

Originally Posted By: d00df00d
Got it. And what is the function of the S-P-Z organo-metallic additives you cited, and of the ashless organic formulas that are displacing them?


Sulfur-Phosphorus-Zinc as in ZDDP, the main Anti-Wear component today.

The other AWs that can displace ZDDP or act as secondary AWs would be the polymer esters, the Ionic Liquids, and the specially synthesized dithiocarbamates.

 

[d00df00d]

Thanks again, Mola!

 

[chrisri]

I know it's not the answer you asked for but maybe someone will be interested . I've used GL4 oil in a box speced for GL5 fluid and had diff whine and loud clicks from diff when pushing car in gear with engine off. But smooth gear changes. With GL5 oil whine when driving is less noticeable and so are clicking sound. Gear change aren't smooth though.

 

[MolaKule]

Clicking sounds can indicate a bad drive pinion bearing or a chipped tooth or both.

This is why you never use a GL-4 rated fluid in a differential speced for a GL-5 lube and vice versa.

 

[chrisri]

I agree but oil change was done by my friend because I was on a trip. What is worrying is that this specification he got from Auto Data and it was wrong. After we found various other wrong informations for various cars both for gearbox and engine oils there. So it's easy for an independent mechanic to make mistake if he uses only this tool for recommended fluid specification.