The speedometer in my 1959 Silver Hawk was wildly optimistic, reading 40 when my GPS said 32. I pulled the gear and "bullet" out of the T10 transmission and counted the teeth - 17. What I needed was a 21-tooth T10 gear and bullet, but they are no longer available. After much research, I determined that the "bullet" from a Turbohydramatic 350 would work, and that there are 21-tooth driven gears available for the TH350. Installed same today and problem solved. Speedometer and GPS agree to within a couple of percentage points.
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Originally posted by GinettaG12P View PostThe speedometer in my 1959 Silver Hawk was wildly optimistic, reading 40 when my GPS said 32. I pulled the gear and "bullet" out of the T10 transmission and counted the teeth - 17. What I needed was a 21-tooth T10 gear and bullet, but they are no longer available. After much research, I determined that the "bullet" from a Turbohydramatic 350 would work, and that there are 21-tooth driven gears available for the TH350. Installed same today and problem solved. Speedometer and GPS agree to within a couple of percentage points.
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The 19 tooth came with the 3.73 rear axle and a 17 tooth with a 3.31 rear axle. The type of driven gear with the "bullet" as you describe it was used on the 1961 & 62 Studebaker T-10's This is a "Chevy style" T-10 which is why the driven gear from the turbo hydramatic fits. The easy thing to do is simply order a gear for a 4-speed Corvette. This is good info if you have a 1961/62 T-10 but if you have a 1963/64 T-10 it uses a different style driven gear.
Originally posted by GinettaG12P View PostThe speedometer in my 1959 Silver Hawk was wildly optimistic, reading 40 when my GPS said 32. I pulled the gear and "bullet" out of the T10 transmission and counted the teeth - 17. What I needed was a 21-tooth T10 gear and bullet, but they are no longer available. After much research, I determined that the "bullet" from a Turbohydramatic 350 would work, and that there are 21-tooth driven gears available for the TH350. Installed same today and problem solved. Speedometer and GPS agree to within a couple of percentage points.Last edited by irish; 07-02-2014, 11:33 AM.sigpic
1962 Daytona
1964 Cruiser
And a few others
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I exchanged a 21-tooth driven gear for the 17-tooth driven gear that was in the car when I bought it. A higher tooth count of the driven gear makes the speedometer cable turn more slowly for a given transmission speed, so I would have thought that a 3.73 rear end would require a higher driven gear tooth count than a 3.31 rear end because with a 3.73, the rear wheels turn more slowly for a given driveshaft rotation than with a 3.31
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Oops! I typed that backwards! I'll correct it.
Originally posted by GinettaG12P View PostReally, the 3.73 had 17 teeth and the 3.31 had 19 teeth? That sounds backwards. A 17-tooth driven gear would turn faster than a 19-tooth driven gear, but a car with a 3.73 final drive would be slower than one with a 3.31 differential for the same driveshaft speed in RPM.sigpic
1962 Daytona
1964 Cruiser
And a few others
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