59 rear axle casting code - NCRS Discussion Boards

59 rear axle casting code

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  • Keith C.
    Expired
    • May 22, 2017
    • 10

    59 rear axle casting code

    my 59 has the codes:
    H167
    3725899 GM 30.


    I assume it is an August 16 1957 date code. Could that be an original unit for an early 1959 corvette?

    Does anyone know how to decipher the 3725899?

    There is no "P" anywhere, so this is clearly not a posi rear end.

    Does the "30" indicate anything?

    Thanks in advance
  • Joe M.
    Extremely Frequent Poster
    • April 30, 1990
    • 1338

    #2
    Re: 59 rear axle casting code

    In my opinion, an August 57 unit would not be original to a 59 car. The "3725899 is the GM part number. The "30" is the mold number used to cast the part.

    Comment

    • Joe L.
      Beyond Control Poster
      • January 31, 1988
      • 43193

      #3
      Re: 59 rear axle casting code

      Originally posted by Keith Conti (63608)
      There is no "P" anywhere, so this is clearly not a posi rear end.

      Thanks in advance
      Keith------


      The GM #3725899 carrier case was used for Corvette non-posi axles from 1957 to 1962. It was also used for passenger cars from 1957 to 1964.
      In Appreciation of John Hinckley

      Comment

      • Keith C.
        Expired
        • May 22, 2017
        • 10

        #4
        Re: 59 rear axle casting code

        Thank you very much for the replies. Is it possible to tell what gears are inside? Also, everything on the car matches 100% except the rear axle. What would be the proper axle date range for a car built in February '59? Is there a good place to keep my eye on for finding the proper axle for the car?

        Comment

        • Joe L.
          Beyond Control Poster
          • January 31, 1988
          • 43193

          #5
          Re: 59 rear axle casting code

          Originally posted by Keith Conti (63608)
          Thank you very much for the replies. Is it possible to tell what gears are inside? Also, everything on the car matches 100% except the rear axle. What would be the proper axle date range for a car built in February '59? Is there a good place to keep my eye on for finding the proper axle for the car?

          Keith-------


          You can get a good idea of what the axle ratio is by counting the number of revolutions of the drive yoke to exactly one complete revolution of the axle. This works whether the ring and pinion gear are the originals installed in this carrier case, or not.

          NCRS guidelines call for the carrier to be dated within 6 months of the car's build date. Any date within that range would be considered correct.
          In Appreciation of John Hinckley

          Comment

          • Keith C.
            Expired
            • May 22, 2017
            • 10

            #6
            Re: 59 rear axle casting code

            Thank you. What would be the proper axle date range for a corvette built in February '59? Is there a good place to keep my eye on for finding the proper rear end for the car?

            Comment

            • Mike E.
              Extremely Frequent Poster
              • February 28, 1975
              • 5134

              #7
              Re: 59 rear axle casting code

              Keith,
              Be aware that a Corvette rear end will have a two-digit code shallowly stamped in the face on the driver's side. Those will be different than the code on a passenger car rear.

              Comment

              • Keith C.
                Expired
                • May 22, 2017
                • 10

                #8
                Re: 59 rear axle casting code

                Great! I found a proper date coded posi rear end case (only) with the thin "P". Will it be easy for me to find all of the internal components to rebuild this?

                Comment

                • Keith C.
                  Expired
                  • May 22, 2017
                  • 10

                  #9
                  Re: 59 rear axle casting code

                  So I found one with a nice clear pic. It's the posi code, proper date code, it has the thin "P". The number "5" is cast to the right of the GM. I don't see any other stamping or castings anywhere?

                  What are the two letters I should look for?

                  Comment

                  • Wayne L.
                    Very Frequent User
                    • September 30, 1981
                    • 233

                    #10
                    Re: 59 rear axle casting code

                    If you look at the housing with the "P" at 3-o'clock, then at 9-o'clock there will be two letters and 2, 3, or 4 numbers stamped near the outside edge of the casting. These characters tell you which plant the assembly came from, the gear ratio, the month and the day of assembly and whether Corvette or passenger car, etc. Stamping will also indicate if the assembly was for a car with "heavy duty brakes", metallic brakes, etc.
                    However, there will be no stamping if the housing was purchased "over the counter".

                    Comment

                    • Keith C.
                      Expired
                      • May 22, 2017
                      • 10

                      #11
                      Re: 59 rear axle casting code

                      Thank you, is there a matrix where I can go to decipher the code? It looks like an A, followed by a "B" then an "8", a "space" then "22".

                      Comment

                      • Wayne L.
                        Very Frequent User
                        • September 30, 1981
                        • 233

                        #12
                        Re: 59 rear axle casting code

                        Keith-
                        There is a matrix for 58-60 Corvette differentials in the TIM & JG (judging manual) and in the GM Corvette parts catalog. The "Corvette and Chevrolet by the numbers" series by Alan Colvin also has extensive information on many drive train components.
                        AB=passenger car with Powerglide transmission, 3.55:1 ratio made at the Detroit Gear & axle plant. The 8-22 means the differential was assembled August 22, which fits nicely with the August 16 casting date.
                        Wayne

                        Comment

                        • Joe L.
                          Beyond Control Poster
                          • January 31, 1988
                          • 43193

                          #13
                          Re: 59 rear axle casting code

                          Originally posted by Wayne Loron (4921)
                          Keith-
                          There is a matrix for 58-60 Corvette differentials in the TIM & JG (judging manual) and in the GM Corvette parts catalog. The "Corvette and Chevrolet by the numbers" series by Alan Colvin also has extensive information on many drive train components.
                          AB=passenger car with Powerglide transmission, 3.55:1 ratio made at the Detroit Gear & axle plant. The 8-22 means the differential was assembled August 22, which fits nicely with the August 16 casting date.
                          Wayne

                          Wayne and Keith-----

                          Keith also needs to keep in mind that the original gear ratio could have changed at some point. By doing the little rotational test I described above he can ascertain what ratio he actually has. For example, if the pinion flange turns just about 3-1/2 times to one revolution of the axle, then he'll know that the differential still has the original gear ratio.
                          In Appreciation of John Hinckley

                          Comment

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