gear oil question

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gear oil question

Postby 289kford » Mon Jun 12, 2017 8:11 am

Are the viscosities the same for any given number for rear axle lube and manual gear box lube? are they obtained on the same scale? Example, 40wt motor oil is has the same viscosity as 90wt at the spec it is measured, but different scales, if I'm explaining correctly.
Bottom line is I see 75-90, 80-90 transmission fluid and 75-90 or 80-90 axle fluid. I always assumed 75-90 is 75-90. Is there a viscosity difference or is it the additives, or is there no difference? I don't know what I put in mine years ago, but my feeling is it probably said axle fluid on the container. I think I'm going to change it to what I know is a GL4 spec that says for transmissions , using either Ford 75-90 conventional XT4QGL or synthetic XTM5QS.
I'm aware of the GL4/ GL5 and syn/nonsyn debates
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Re: gear oil question

Postby zray » Mon Jun 12, 2017 12:48 pm

Off topic

Anyone here had verifiable damage from GL-5 in a toploader or T-10 ? Try as I may, I can't get any synchro damage from my habitual usepage of Mobil 1 75w-140 LS . I use it in the trans. and the pumpkin. You'd think after 150,000 (hard) miles on the toploader, there would be some indication the GL-5 was killing the brass parts.


Despite internet hysteria to the contrary, my brass synchro rings have not evaporated, nor do I miss a shift when sheifting fast. The 'danger' to yellow metals from commercial gear oils was recognized and eliminated around the time of WWII. *


There are many who want to believe its still real. It makes for good hysteria for those who have never heard of, or know little about the issue.

BTW, synthetics helped my T-10 and toploader shift better.


*. Leaned that from a grad US Army Petroleum School, Ft. Lee, VA

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Re: gear oil question

Postby 289kford » Mon Jun 12, 2017 2:06 pm

I found it interesting that the Ford literature for the synthetic version does not say what GL# it is but does say " and is also recommended for older transmissions including rear wheel drive that recommend GL-3 and GL-4 type gear oils" while the conventional fluid is GL4.
I'm not so much worried about that. My concern was that the Ford lubes (at least now) are specific to axle or trans.
I tried to look up the trans fluid part number from the owner guide, it is non-existant and I could not even find a reference to it. I will look at my guide again and see what it says for the rear end.

"BTW, synthetics helped my T-10 and toploader shift better."
That would be a plus for me if changing the fluid helps. I know it's not an overhaul in a bottle, but I've got some notchy 2nd gear shifts and if I have the wrong fluid I'm not helping it.
Edit
As found in the parts catalog
Trans CR3Z 19C547 B extreme pressure SAE 80
Axle C1AZ 19580 E or F
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Re: gear oil question

Postby zray » Mon Jun 12, 2017 8:05 pm

You could experiment with 75w-90 vs. 75w-140 and see if one is a better performer than the other.


I use the Mobil 1 75w-140as it's better suited for protection when the transmission or rear end is subjected to hard usage, which for me is long distances at high speed. I probably should look into coolers.

It figures that the 75w-140 is more costly than the 75w-90

The brand I prefer also comes with LS additives, which is nice for the rear end, although I do add some Motorcraft LS additive anyway.



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