I am trying to get some confirmation on which transmission I have and my numbers do not seem to match what I have read in literature. Maybe I am reading the numbers wrong (they are pretty worn) or hopefully someone has some can help me decipher what I have. It is a 3 speed in a 1956 3200 with a 235 engine. I’ll try to post pictures below. On tail piece, left hand side: GM 18 3(8?)707185. On case, left side: GM 12 38(6?)45122, then under that, C266. On side cover: 9845157. Sorry, the picture will be upside down as the stamp is upside down on the side cover (never mind that I could not figure out how to flip it).
3845122 is the casting number of the transmission case for the 1955-1957 3 speed transmission for passenger cars and Corvettes (found in an Internet search)
I see in an ebay post from your link that the 384... number is for a muncie 3 speed, and the one shown for sale also has the tail housing number that matches mine, but the cover housing number does not. Not sure what all that signifies, or how common those casting numbers where used in muncie 3 speeds.
That is the stock SM318 3 speed transmission with the date code for that year. Very common for cars & trucks of that era. The tail shaft and side cover numbers don't always match as a lot of repairs and interchanges occur over the years. Fred
1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes 1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes 2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans 1947 Willys CJ2A w/F-Head engine
Your Tail Shaft Extension number is 3707195 and the case number 3845122 were used on 3-speed Cars, Corvette's and Trucks from 1955-59, as Fred said...very common.
You got the date code right...
Mike B
Mike Boteler
1956 Chevy 3100 Resto Rod 1952 Willys M38 Army Jeep 1983 Jeep CJ7 Laredo 1984 Jeep CJ7 +++++ Silver Spring, MD
