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rotorwrench · 03-07-2021, 10:34 AM

The original Lincoln Mercury Overhaul Manual lists the oil capacity for the different transmissions used from 1949 thru 1951 but it is listed by fluid weight and not by liquid volume measure. The 1949 thru early 51 Mercury overdrive transmission capacity is listed as 3 1/2 lbs. I used one of the calculators for weight to volume (pounds to cups) for lubricating oil and it came out to 3.8 pints. Many times this can be problematic so I have always filled very close to the lower edge of the filler plug hole. I use AeroShell 100W motor oil with no Lycoming additive for my transmissions. It's pretty warm here in Texas so I use this to keep the viscosity near straight grade SAE-90 gear lube. The Sta-Lube GL-4 is fine as mentioned previously by Mac. The GL-4 is the replacement for the original GL-3 mild EP specification that was called out in the manufacturer's recommendations. There are enough carry through openings between the transmission and overdrive sections to allow fluid level equalization but, as Mac stated, it's not a bad idea to put some in the OD section if you are planning on driving the car as soon as the oil change is finished.

03-07-2021, 10:34 AM	#4
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,457	Re: Early '51 Merc. overdrive Transmission The original Lincoln Mercury Overhaul Manual lists the oil capacity for the different transmissions used from 1949 thru 1951 but it is listed by fluid weight and not by liquid volume measure. The 1949 thru early 51 Mercury overdrive transmission capacity is listed as 3 1/2 lbs. I used one of the calculators for weight to volume (pounds to cups) for lubricating oil and it came out to 3.8 pints. Many times this can be problematic so I have always filled very close to the lower edge of the filler plug hole. I use AeroShell 100W motor oil with no Lycoming additive for my transmissions. It's pretty warm here in Texas so I use this to keep the viscosity near straight grade SAE-90 gear lube. The Sta-Lube GL-4 is fine as mentioned previously by Mac. The GL-4 is the replacement for the original GL-3 mild EP specification that was called out in the manufacturer's recommendations. There are enough carry through openings between the transmission and overdrive sections to allow fluid level equalization but, as Mac stated, it's not a bad idea to put some in the OD section if you are planning on driving the car as soon as the oil change is finished.