| 35gal | -- 08-03-2010 @ 5:55 PM |
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A year ago I put 3:54 gears in my 34 and was told that the in order for the speedometer to work accurately, I would need to put an 18-tooth gear in the speedometer gear turtle. It seem to work fine. Now I’m putting 3:54 gears in my 35 and would like to modify the speedometer gear turtle, but I’m confused. My 35 manual states that the drive gear turtle should also be 18 teeth. How can that be the same as a 34 since the 34 car has bigger tires then the 35. I would think the diameter of the tire would make a difference in the speedometer reading.
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| 37RAGTOPMAN | -- 08-04-2010 @ 8:07 AM |
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I think your speedometer is where the difference is, the 34 has one set of gears in it for that tire size where the 35 has a different gears in the speedometer,for its tire size, these were made to go with the tires size the car came with, were are you getting the 18 tooth drive gears,35 and up are different then the 34 and down . hope this helps 37RAGTOPMAN KEEP ON TRUCKIN,,,,,,,,,
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| supereal | -- 08-04-2010 @ 9:51 AM |
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The 3:54 rear requires the 18 tooth speedo drive gear, while the 3:78 uses the 19 tooth type. 4:11 is 21. The driving gear on the driveshaft is the same for all. C&G has the 18 tooth gear (AA-17271-E), but you will have to adapt the "turtle" to accept the gear and the torque tube to get the correct mesh, as the housing is not reproduced. Most of these gears assumed 16 inch wheels. I haven't seen many, if any, old car speedometers that are accurate. The NOS speedo in my '47 is about 8 mph off, even with the correct drive. Knowing that, I just mentally adjust my speed.
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| 35gal | -- 08-04-2010 @ 10:20 AM |
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I have the 18 tooth gear already that I got from C&G. And yes I know that the turtle housing will have to be sanded down for the gears to mesh. Does anyone know if the turtle housing for a 3:78 ratio would be the same as the housing for a 3:54. According to my book the 3:78 takes a 19 tooth gear. That's just one tooth more. Maybe the housings are the same.
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| supereal | -- 08-04-2010 @ 12:40 PM |
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Try it and see. The housings are made for the number of teeth stamped on the top of the housing. The gears with the smaller amount of teeth tend to be a slightly smaller diameter, but often work if the housing matches the diameter of the torque tube.
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