My insurance co. has sent a letter stating because I can't verify my mileage on my Model A that I won't be eligible for the resticted mileage low rate I have been getting. So an after market speedo is going in. I would like to buy a mechanical one due to the cost of the speedo and the sender on the electric. I have a turbo 350 and even saved the cable and stuff. But with a 3.42 rear and 16 inch tires how do I attempt to get this thing to read right. Can I change the drive gear in the trans and how do I determine which one I need??? Thanks
wtf are they gonna do send someone to you house every year to check it? id look for another insurer....got the same restriction on my policy but ive never been asked to prove it
Here's a calibration page for when you have a basic setup... Find a GM ch***is parts book including cars with TH 350. There's a chart covering tire size and gear ratio to find correct gears...but you will have to measure your tire and then find out what tire on the chart matches that diameter, since 16's won't be covered. Tires are listed by size designation, not diameter, so you'll need a tire size chart to translate.
Forgot the calibration page: http://www.speedometershop.com/rep-pag.htm Note that an available but more expensive way is to count turns on what you have, then order a ratio converter gearbox.
Drive as fast as you can down the interstate until a trooper catches up to you. I'm pretty sure he'll tell you exactly how fast you were going. They're good about that.
That page reminded me--look at the description to determine if your speedo drive parts are from a Buick or Chevrolet built TH350! Totally different housing for driven gear, and either could be on any particular trans after a few rebuilds. TCI also gives some good translation data for the archaic G-70 type tire sizes you will find in old GM parts catalogs.
I think that this subject is being over complicated. Hook up the speedometer and using the odometer drive exactly 10 mi. See what the odometer reads and plug it into the following formula.X/10=N/OD. 10 is the actual miles driven,X is the actual gear size needed,N is gear teeth in trans , and OD is the distance shown on your odometer. Plug the numbers and solve for x by cross multiplying. The tire size ect. is not needed this way. It will get you close enough to solve your problem.
how is it overcomplicated getting the right gears in the speedo drive the first time by using a simple calculator ?
With an electric speedo you don't have to go through all the BS shown above. I got an electric in two cars and think they are great.
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