transmission oil weight

[ahshoe]

Got a 3-speed manual transmission that I just installed on my '56 F100, 272 c i "Y" block. I am ready to fill with 80-90w. But not sure what GL to use. Any recommendations?

 

[50fordcoupeman]

I have always been told to run GL-4 in this era of manuals because of the brass parts within.

 

[wellcraft17]

I use tractor supply 90wt mineral oil, yellow metal friendly

 

[dmsfrr]

Just sharing these words from this link...
(and assuming Ford used similar transmission parts in various vehicles from the same era)

"The recommended oil for an overdrive transmission is 90W Mineral GL1 gear oil. Modern gear oil with higher GL ratings should not be use because some of the additives are corrosive and could be detrimental to the brass components.
The synchronizer blocking rings in standard three speed and three speed overdrive transmissions are brass."

https://www.ctci.org/gilsgarage/OverdriveTransServicing.php

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