replacing my tranny and found the drive gear is broken. its a 19 tooth that i put in when i changed the tires, forget what tooth it had but i think it was green. that is the way you you recalibrate the speedometer right, if the speedometer is off when you go to a different size then you change out the gear, some times for one with more teeth and some times on with less teeth.

 

thank you for talking about this.

yes, the driven gear is how you recalibrate the speedo.

the drive gear is the one inside the tranny that spins the driven gear.

less teeth on the driven gear speed up the tranny, more teeth slow it down.

larger tires slow down the speedo and smaller tires speed it up.

i have to ask you, what car do you have, what tranny, and how many teeth are on your drive gear (6,7,8, or 9)?, if you don't mind me asking.

thank you.

 

i have a 1970 mustang with a c4 tranny. not sure of the rear end gear ratio but im running a 19 tooth gear on the end of the cable and its pretty close to the right speed. if im reading, say 5 miles lower on the speedometer than im really going do i go with more teeth or less.

 

if your speedo is reading too slow, thengo with less teeth on the driven gear at the end of the cable. you can determine your exact gear with some calculations that i can provide if you need it, but since you don't know your gear ratio you can guestimate the gear you need. they are cheap enough. you can even find out the gear ratio in your rear by doing some stuff if you want to know.

 

Where can you go about finding a gear for a c6 with 4.10s?

 

try a reducer. factory 4.10 or 4.30 cars had reducers at the end of the cable to use the appropriate gear. or mabey a 23 tooth gear might work. thats as high as they go but the teeth are thin so it won't last forever.

 

well its an open diff. the only way i know to find the ratio with it it to tape a string on the driveshaft and push the car forward one revolution of the tires and count the number of times the string warped around the driveshaft. that requires putting the car on the ground. if you know of some othewr way that will work let me know.

 

i know i am real late on this one, but i havn't been on this forum for a long time. what you'll have to do is jack one tire off the ground and rotate the tire 10 full turns while looking at the driveshaft to determine how many turns it completes. I usually mark the driveshaft and the tire and have someone turns the tire 10 times or look at the pinion yoke. but anyway, take the number of driveshaft turns and divide it by half the tire turns. for example, if i turned the tire 10 times and yielded 20 turns on the driveshaft, i would divide 20 by 5 and get a ratio of 4 to 1, so a 4.00 gear ratio. This is for an open differential only.