Speedometer Accuracy Issues...Driven Gears
Thread Starter
Racer
Joined: Apr 2013
Posts: 302
Likes: 16
You need fewer teeth on the driven speedo gear to make the speedometer read 'faster'. For the amount of error you have, I would go with 3 fewer teeth than what you have now.
These gears come in "sets". For each 'drive' gear, there are several 'driven' gears that will work with it; and each drive gear MUST have driven gears within a specific range of teeth. You can't go any more or less than what the drive gear will allow. I'm pretty sure that you can get a 19 tooth driven gear for your 'set', but you need to research that to be sure.
These gears come in "sets". For each 'drive' gear, there are several 'driven' gears that will work with it; and each drive gear MUST have driven gears within a specific range of teeth. You can't go any more or less than what the drive gear will allow. I'm pretty sure that you can get a 19 tooth driven gear for your 'set', but you need to research that to be sure.
I went back to the 22 teeth gear and the speedo reads faster.
Race Director
Joined: May 2006
Posts: 18,731
Likes: 2,582
From 4.56 to 3.31 the Drive gear is 6261794.
Starting with the 3.08 and down the drive gear can be 3924099 or 6261794. The majority in the second group are the 3924099. So you may have the wrong Drive gear for a 3.08.
The 3924099 was superseded by 3905494.
Starting with the 3.08 and down the drive gear can be 3924099 or 6261794. The majority in the second group are the 3924099. So you may have the wrong Drive gear for a 3.08.
The 3924099 was superseded by 3905494.
Last edited by MelWff; Jun 16, 2020 at 11:43 AM.
Thread Starter
Racer
Joined: Apr 2013
Posts: 302
Likes: 16
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Think of it this way: with a [drive] worm gear turning a fixed speed, a mating [driven] gear with 12 teeth will take longer to make one revolution than a gear with 10 teeth. So more teeth on the driven gear will slow down the speed; less teeth will make it go faster (higher MPH).
I suspect that the 18 tooth gear was below the acceptable range for your drive gear. You just need to crawl under the car, remove the speedo gear 'bullet', and use the mirror to see what color the drive gear is. If the gear you have will accept a 19 tooth drive gear, that will improve the speedo accuracy without having to pull the trans tailshaft.
I suspect that the 18 tooth gear was below the acceptable range for your drive gear. You just need to crawl under the car, remove the speedo gear 'bullet', and use the mirror to see what color the drive gear is. If the gear you have will accept a 19 tooth drive gear, that will improve the speedo accuracy without having to pull the trans tailshaft.
