VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Help ID differential

Found on the local Craigslist and wondering if it is what he says. Aren't most cast in numbers used by GM basically a letter for month then three to four numbers for day and year? In this case it is F (June) 2 (day) and 47 year? That's my inexperienced thought anyway. There is also what I think is a part # 3725899 and a hand stamped # AA 7 08. He says it is stamped 3.70:1 geared. I have been thinking about going to the later open driveshaft. I don't remember where I got the info but I have wrote down that 55-64 chevy cars have the same 60" wheelbase.

The only years a 3.70 was ofered was 1955 and 1956 with standard trans or mid 1959 and up with overdrive.
AA is the base ratio so would be 3.70 in 1955 and 1956, 3.55 in 1957 and up.
The ratio was not stamped on the case....have him count teeth.
Case caring number is 1955-1956.

Thanks Gene but what about the 3725899 or the F247 do those #'s tell us anything? Maybe instead of F(June) 2 (day) 47 year it might be June 24 with the 7 being 57??? He's advertising it as a 1957. I haven't called him yet but he says it is stamped 3.70:1, a latter model ring gear I have is stamped with the ratio. I will call him, he is about two hr. away so I don't want to make the trip without knowing exactly what it is and if I go, to know about it when I'm looking at it. He is also selling a driveshaft from a 1957 and say's 53.5" is the stock length for a powerglide trans.

3725899 was used in 1958 production from Nov 1957-and up for 1958 production.
One drive shaft fit alll 1955-1957 models and transmissions.
The

f247 doe not match any codes and code did not indiacte year, only day and month.

Hmmm, At that time did the 58's start in Jan.? I worked for GM from 75-06 we had model change in the summer before the new year. I've yet to contact the seller.