Gear oil for our GMC's. Yellow metal safe?

[Gunfreak25]

I used to think gear oil was gear oil until I did some reading of my own. It seems that a lot of todays gear oils use detergents that actually eat up the metal parts inside certain gear boxes. The metals at risk being "yellow metals" that many old vehicle gear components contain. Even the M35 guys strictly warn against using non yellow metal safe gear oils.

I was just wondering if our GMC's have to follow the same rule of sticking with a "yellow metal safe" gear oil. Seems to me like they would. Although I have not been able to find any information to support this, and it seems like a very valid question to ask regarding the maintenance of our GMC's.

 

[paulfarber]

Use a good GL-5/MT-1 (that's the actual label).

Most, if not all gear lubes are 'yellow metal' safe. The 80/90 wt oils don't get hot enough to make the acids (combination of water, sulfur and heat). About 20-30 years ago this was a problem, not any more.

The GL-5 spec does have a test for yellow metal corrosiveness.

 

[cbvet]

Do you know whether modern GL-5/MT-1 is compatible with the GL1 currently in a Deuce trans?
Seems like someone said they shouldn't be mixed.

 

[Gunfreak25]

Thanks Paul. So as long as the container is marked MT1 it does not matter if it's GL1 or GL5. Because I know there are a lot of GL5 lubes that are not yellow metal safe. Here are some good threads on the subject.

http://www.steelsoldiers.com/deuce/41187-wwhat-does-term-yellow-metal-mean.html

http://www.steelsoldiers.com/deuce/47921-gl-1-gear-oil-alternative.html

 

[M215]

NAPA sells GL-1 straight 90 gear lube, that is all that I use. Why take a chance?
Karl

 

[Gunfreak25]

That's what i'll be going with as well, I don't plan to be driving the trucks thousands of miles a year anyway so GL1 should be fine. Does it come in 140W?