Brendan - Unlikely to have been a '49 as the "Crash Box" which we confirmed by the casting codes was replaced by the SM420 by then. I did some digging in the GM Heritage Archives and found the "PM" serial number prefix Utah John posted above is actually associated with 1946 Chevy 1/2 and 3/4 ton truck as RPO 318 (4 speed option) for that year. Looks like he has an original to his truck transmission. wink

Best SWAG considering the casting date codes on the case and top cover on your 4 speed is it make me think your transmission is a very late '39 or early '40. The serial number will be the tell all I think.

BTW - The "GEA" engine prefix was used on 1949 6000 series trucks according to the 1949 Chevrolet Truck Data PDF, but "PM" prefix not used on an transmissions that year so very likely from two completely unrelated trucks.

Let me know what you find on your serial number and we'll hunt more details down. wink

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)