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Hi everyone, I am trying to figure out what rear end is in my car. the casting number is 8780614, with GM 6 above this number. Would I be able to determine what gear is in the differential by this number alone? I have looked for a stamp number but cannot seam to find one. Also what book would be a good source to purchase to find this information? Scott member # 40610
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Re: 59 rear axle / differential
Scott -
Must be a passenger car center section or axle assembly - that casting number (probably 3780614, not 8780614) was never used in a Corvette. The ratio and date code are stamped on the forward-facing portion of the passenger side of the casting, on a rough-cast surface, at about 8 o'clock looking rearward at the center section (very hard to see, if at all, without careful cleaning). There should be a date code cast adjacent to the casting number as well. The new "Corvette By The Numbers" book, by Alan Colvin, is an excellent resource for obscure component detail identification. -
Re: 59 rear axle / differential
Scott-----
As John mentioned, there was no 8780614 differential center section casting. However, GM casting #3790614 was a casting used for 1962-63 Chevy IIs differential center sections for BOTH standard and posi. "3", "6", "8" and "9" are easily confused in reading casting numbers.
The vast majority of Chevy IIs of the 62-63 period were fitted with 3.08:1 or 3.36:1 rear gear ratios. A smaller number were fitted with 3.55:1.In Appreciation of John HinckleyComment
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Re: 59 rear axle / differential
Joe -
Trivia you might enjoy on the old Chevy II ("Fisher Falcon") axles - when I was a production Foreman at Willow Run in 1964-1965, building the old Chevy II (and Corvair) together, I ran the Motor Line and Chassis/Body Marriage Line. Even though the old Chevy II was a "schoolteacher's car" of the day, the available axle selection was incredible; between ratios, posi/non-posi, and organic-vs.-metallic brake linings, I had 48 different part numbers of Chevy II rear axle assemblies to schedule. "You can have it your way" was in effect at Chevrolet long before Burger King.
The Chevy II axle proliferation was exceeded only by the number of as-shipped engine assemblies I had to deal with; we had 128 part numbers of engines between the two car lines, over 110 of which were for the Chevy II (L-4, L-6, and V-8). Chevy never missed an opportunity to meet an obscure customer's needs and sell another car - we even had a "High-Altitude Low-Compression Brazilian Police" engine; I think we only got six the whole model year, and I'm sure we mis-used them and substituted some other flavor when the weird Brazilian cars came down the lineComment
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Re: 59 rear axle / differential
Your talking about the pumpkin , not the banjo , the pumpkin should first have a large P casted in it if it's a posi. The GM 6 your talking about is just a casting number. All cast iron parts would have this marking GM? the number is to identifies which mold the part was casted in. Many molds were used to cast the same part and each mold had a number like GM1 or 2or 16.The reason was that if a casted part was bad the supplier would know which numbered mold was no good.Comment
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Re: 59 rear axle / differential
John------
Yes, all of the drivetrain options in days of yore were one of the things that made cars so exciting then-----you could "customize" your car on the order form and end up with a pretty unique vehicle. In fact, considering the total number of options available, just about any car could be unique.
The fact that the different car lines in GM had their own, exclusive engines (something that Ford and Chrysler Divisions never had) also made things exciting. When you favored a particular car line, you favored all of its individuality which included engines and, sometimes, even transmissions. There was a real difference between car lines even if the chassis shared components.
Today, that's mostly gone. GM makes engines the way that Ford and Chrysler always have---at the corporate level for all car lines. It's efficient and it is consistent with delivering good value to the customer, but a lot of the personality and individuality has been taken out of the cars.In Appreciation of John HinckleyComment
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