i installed an autometer speedometer and odometer. it works but i clock about 1.3 miles for every mile i drive.

i understand that to get the driven gear (pinion) with the number of teeth i need, i use the fromula - drive gear x axle ratio x tire revolutions per mile, divided by 1000. i have pulled the cable and removed the driven gear.

how in the world do i count the number of teeth on the drive gear that is inside of the transmission.

i have a 67, c4, and a 3.00 rear. is there a place i could go to look up the number of teeth on the 67, c4, with a 3.00 rear?

i checked our faq but did not find one that addressed my specific problem.

 

Probably an 8 tooth. You could look through the little hole and mark one tooth with a marker then turn the shaft...mirrors and patience.

 

Ford drive gears are machined into the output shaft on the C4. You will need to remove the tail housing to determine how many teeth your transmission has.

 

well, let me ask this. since my odometer tells me that i have gone further than i have gone, do i need more or fewer teeth on my driven gear to help correct the problem. it seems to me more is the answer. like in a rear end, the more teeth on the ring gear, the lower the gear ratio.

 

Here is some information you need to know.
http://www.z31.com/speedo.shtml

 

[quote]ORIGINAL: jroseman

i installed an autometer speedometer and odometer. it works but i clock about 1.3 miles for every mile i drive.

Maybe it's Canadian.

 

Yeah, you need more teeth.

 

i changed from 19 to 20 teeth - took it down the road and watched the mile markers - it seems to be very close now - at least as close as i'm going to get it. i'm more concerned about the odomoeter than the speedometer but i will check that tomorrow. thanks.

 

If the odometer is right the the speedometer will be right.