58 4-speedo gear - NCRS Discussion Boards

58 4-speedo gear

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • Jerry DiTullio
    #1

    58 4-speedo gear

    I am installing a 3:70 posi in my 1958. Does anyone know the correct teeth count for the speedo gear for a 4-speed? Corvette America lists may differnet teeth counts and colors, but doe snot indicate whcih goes with which rear end ratio.

    Thanks
    Tags: None
      • Top
    • Joe L.
      Beyond Control Poster
      • February 1, 1988
      • 43193
      #2
      Re: 58 4-speedo gear

      Jerry-----

      The simple answer is that you need a GM #3708699 speedometer DRIVEN gear. This is a 22 tooth GREEN gear. It's GM discontinued but, I believe, available in reproduction. Unfortunately, though, the simple answer is not likley to be the correct answer. There are just too many variables with respect to speedo gears.

      First of all, in order to use the above-referenced driven gear, you have to have the correct DRIVE gear installed. That gear is a steel gear of GM #3708144 with an OD of 1.85". If you have a steel gear of GM #3708145 with an OD of 1.77" installed, then the 3708699 will not work.

      Another factor is installed transmission. If you have an original 1958 (or, 1959-60) Borg-Warner T-10, then the above applies. If you have a later T-10 or a Muncie installed, everything changes.

      Yet another factor is tire size. The above-referenced only applies if you're using original tires (or, tires with very close to the same OD). If that changes, then everything goes "out-the-window", too.
      In Appreciation of John Hinckley
        • Top

        Comment

        • Jerry DiTullio
          #3
          Re: 58 4-speedo gear

          Joe,
          I have a T10 in the car (original) and original size tires. Is the metal gear in addition to a colored gear also in the speedo unit?
            • Top

            Comment

            • Joe L.
              Beyond Control Poster
              • February 1, 1988
              • 43193
              #4
              Re: 58 4-speedo gear

              Jerry-----

              The steel gear is contained within the transmission and is an interference (press) fit on the transmission main shaft. It is the gear which drives the nylon gear and with which the nylon gear must mesh. If it has to be changed, then the transmission must be removed from the car and partially diassembled.

              You can infer which DRIVE gear that you have in there now by determining which DRIVEN gear is currently installed and what the current rear gear ratio the car has.

              If a DRIVE gear change ends up being necessary and you want to avoid that, you can use your existing gears with an external adapter which modifies the output speed of the gears.
              In Appreciation of John Hinckley
                • Top

                Comment

                Previous template Next
                Working...

                Debug Information

                Searching...Please wait.
                An unexpected error was returned: 'Your submission could not be processed because you have logged in since the previous page was loaded.

                Please push the back button and reload the previous window.'
                An unexpected error was returned: 'Your submission could not be processed because the token has expired.

                Please push the back button and reload the previous window.'
                An internal error has occurred and the module cannot be displayed.
                There are no results that meet this criteria.
                Search Result for "|||"