Does Gear Oil Degrade Bronze?

[Roberts210]

I've heard about this for years, but I've yet to read anything authoritative. Are certain gear oils bad for yellow metals? Reason I ask is I have an old Chevy overdrive unit that has bronze thrust washers in it and I don't want to use the wrong gear oil and eat 'em up. Anyone know for sure?

 

[ChrisLS8]

GL5 will, Nissan uses bronze synchros in their older transmissions and that fluid causes mayhem in them

 

[rlitman]

My understanding is that the issue comes from the sulfur in the EP additive package that protects sliding type gears (hypoid). Yes, some gear oils are bad for bronze.

 

[1/2 Cup]

My understanding is that the issue comes from the sulfur in the EP additive package that protects sliding type gears (hypoid). Yes, some gear oils are bad for bronze.

As above...

 

[noid]

I think this is what you might be looking for:

http://www.rtsauto.com/wp-content/uploads/2016/12/Transaxle_oil.pdf

TLTR; dont use GL-5 in GL-4 applications even if the bottle says its backwards compatible.

 

[Roberts210]

Thanks guys.

 

[Wakefield]

I understand that in some cases using a higher GL number than is called for is bad because the stronger EP additives are corrosive.

Can a broken in rear end run a lower GL # than a new one (that is harder to lubricate because it hasn't broken in yet)?

 

[Wakefield]

I guess a related question would be whether modern motor oil would damage the old fashioned babbit bearings found in original old cars such as the 1930's Dodges (because of too aggressive additives) I wouldn't think motor oil would be as aggressive however as hypoid oil

 

[noid]

I guess a related question would be whether modern motor oil would damage the old fashioned babbit bearings found in original old cars such as the 1930's Dodges (because of too aggressive additives) I wouldn't think motor oil would be as aggressive however as hypoid oil

Chevron and Napa still sell GL-1 oils; best to run those in that sort of application.

 

[Ole Slewfoot]

Dont confuse GL with oil weight.

API Gear Oil Specifications
Spec Status Description

GL-1 Active The designation API GL-1 denotes lubricants intended for manual transmissions operating under such mild conditions that straight petroleum or refined petroleum oil may be used satisfactorily. Oxidation and rust inhibitors, defoamers, and pour depressants may be added to improve the characteristics of these lubricants. Friction modifiers and extreme pressure additives shall not be used.

GL-2 Inactive The designation API GL-2 denotes lubricants intended for automotive worm-gear axles operating under such conditions of load, temperature, and sliding velocities that lubricants satisfactory for API GL-1 service will not suffice.

GL-3 Inactive The designation API GL-3 denotes lubricants intended for manual transmissions operating under moderate to severe conditions and spiral-bevel axles operating under mild to moderate conditions of speed and load. These service conditions require a lubricant having load-carrying capacities exceeding those satisfying API GL-1 service but below the requirements of lubricants satisfying API GL-4 service.

GL-4 Active The designation API GL-4 denotes lubricants intended for axles with spiral bevel gears operating under moderate to severe conditions of speed and load or axles with hypoid (see note)gears operating under moderate speeds and loads. These oils may be used in selected manual transmission and transaxle applications where MT-1 lubricants are unsuitable. The manufacturer's specific lubricant quality recommendations should be followed.

GL-5 Active The designation API GL-5 denotes lubricants intended for gears, particularly hypoid (see note) gears, in axles operating under various combinations of high-speed/shock load and low-speed/high-torque conditions.

GL-6 Inactive The designation API GL-6 denotes lubricants intended for gears designed with a very high pinion offset. Such designs typically require protection from gear scoring in excess of that provided by API GL-5 gear oils.

MT-1 Active The designation 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 service provide protection against the combination of thermal degradation, component wear, and oil-seal deterioration, which is not provided by lubricants in current use meeting only the requirements of API GL-1, 4, or 5.

You can download API's Publication 1560 on gear oils for more detailed inform

 

[Roberts210]

I read the pdf, and he's talking Corvairs, and comparing today's oils to '60's oil. The O.D. unit I've got is late '40's early '50's technology. There are no brass synchros, but there are 1/8th inch thick bronze thrust bearings. Interestingly enough I mic'd two of the thrust bearings that were broken. One mic'd at .120 and the other mic'd at .113 They aren't red tho.

 

[WittHay]

I think in old manual transmissions the trucks used the 90W with the EP additives for low speed, high torque and the cars/light duty pickups used 90W mineral oil where the wear occurs at higher speeds. If it has a overdrive, I would try and find some GL-1 90W gear oil

 

[Roberts210]

The 3-speed and the O.D. have separate gear boxes. Thanks for the tip. I've got GL-1 90 wt in the 3-speed, but haven't filled the O.D. yet.

 

[Lelandwelds]

Nothing is ever simple I suppose.

There are a bunch of different bronze alloys. All the low zinc alloys are pretty corrosion resistant. The aluminum and silicon bronzes are very sulfur resistant. The leaded brasses like naval bronze are corrosion resistant esp in salt.

Companys play with composition or just shoot for a range that varies.

 

[MShaw]

"I guess a related question would be whether modern motor oil would damage the old fashioned babbit bearings found in original old cars such as the 1930's Dodges (because of too aggressive additives) I wouldn't think motor oil would be as aggressive however as hypoid oil"

The short answer is that older engines without filters should use non detergent oil. The detergents carry the contamination in suspension to the filter. Without a filter the contamination is recycled thru the engine rather than settling to the bottom where it is removed at drain time.

 

[2oolhound]

Nothing is ever simple I suppose.

There are a bunch of different bronze alloys. All the low zinc alloys are pretty corrosion resistant. The aluminum and silicon bronzes are very sulfur resistant. The leaded brasses like naval bronze are corrosion resistant esp in salt.

Companys play with composition or just shoot for a range that varies.

Why do you have to go and make things so complicated?

This thread reminded me of Avril Lavigne's song "Complicated" LOL How many grades of 90 wt were around when this equipment was made? I suppose there is one superior grade but man we sure have to do our homework these days.

Phosphor bronze is a common material used in transmission gear bushings. These bushings breath oil. Put a new bushing down on a small puddle and watch the oil get absorbed. The bushings must be made on precision lathes with ultra sharp tools so the pours aren't glazed shut in manufacture.

 

[finn]

"I guess a related question would be whether modern motor oil would damage the old fashioned babbit bearings found in original old cars such as the 1930's Dodges (because of too aggressive additives) I wouldn't think motor oil would be as aggressive however as hypoid oil"

The short answer is that older engines without filters should use non detergent oil. The detergents carry the contamination in suspension to the filter. Without a filter the contamination is recycled thru the engine rather than settling to the bottom where it is removed at drain time.

I don’t think many lubrication engineers or tribologists would agree with you.

 

[2ndGearRubber]

My understanding is that the issue comes from the sulfur in the EP additive package that protects sliding type gears (hypoid). Yes, some gear oils are bad for bronze.

Yup, the issue is the friction modifiers.

Syncros need friction, GL5 reduces it. People then believe GL5 hurts the bronze, chemically, when really it's the friction modifiers making the syncros work harder.

 

[georgiadave]

There are gear lubes that address the bronze issues and syncro friction needs. Redline MTL and some of the Corvette compatible lubes come to mind.

 

[Packard V8]

The short answer is that older engines without filters should use non detergent oil. The detergents carry the contamination in suspension to the filter. Without a filter the contamination is recycled thru the engine rather than settling to the bottom where it is removed at drain time.

FWIW, I first saw the above in a Tom McCahill article in Mechanix Illustrated around 1962.

I don’t think many lubrication engineers or tribologists would agree with you.

jack vines