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rotorwrench · 10-17-2020, 09:44 AM

GL3 rating was updated to GL4 rating many years ago. It is still a mild EP and mild EP lube was recommended by Ford for the overdrive transmissions of the late 40s & 50s. While synchro blocker rings are yellow metal, they aren't as soft as the phosphor bronze bushings used in the early transmissions. Most of the worry was about the bushings and thrust washer in there. Mild EP is fine but no-EP lubes like GL1 will work OK if the vehicle is driven lightly like most antique vehicles are.

I still use Aeroshell W100 motor oil with no plus designation for my old transmissions. It is expensive but it's good stuff. It's an SAE 50 motor oil that has the same viscosity as straight SAE 90 gear lube. A person can use GL5 in the rear axle since there are no bushings in there.

10-17-2020, 09:44 AM	#4
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,422	Re: Toploader installation. GL3 rating was updated to GL4 rating many years ago. It is still a mild EP and mild EP lube was recommended by Ford for the overdrive transmissions of the late 40s & 50s. While synchro blocker rings are yellow metal, they aren't as soft as the phosphor bronze bushings used in the early transmissions. Most of the worry was about the bushings and thrust washer in there. Mild EP is fine but no-EP lubes like GL1 will work OK if the vehicle is driven lightly like most antique vehicles are. I still use Aeroshell W100 motor oil with no plus designation for my old transmissions. It is expensive but it's good stuff. It's an SAE 50 motor oil that has the same viscosity as straight SAE 90 gear lube. A person can use GL5 in the rear axle since there are no bushings in there.