Well I really screwed my speedometer up! I changed my gears from 2.72 to 3.73 and I added larger tires(30" Outter diameter), how would I calculate the new speedo gear needed?

 

Find a mesured mile, such as a highway mile marker. Reset the trip odometer to zero. Drive the mile and see what the odometer has registred. Find the percent error between what the odometer indication and the actual mile you have driven. Ex if the odometer indicates 1.3 mile, the error is 30% fast. Remove the speedo gear at the transmission & count the theet. Since the cable is turning 30% too fast you want to slow it down by 30%, so replace the speedo gear with one that has 30% more theet. The real fun is to find the gears.
Easy way, take the car to a shop that specializes in spedometer calibration. Check with the Highway Patrol people & find out who calibrates their spedometers.

 

Well I got a catalog and a store by my house that has these gears. I was wondering if there was a formula? Well I know there is one, but I don't know what it is.

 

Try www.speedometersolutions.com
Give them all your info and they will tell you. You will need the gear and the holder because there is a short and a long one.

 

I FOUND IT!!!

Tire revolutions per minute = 63360/(Tire outside diameter in inches) X 3.14159

Driven Gear teeth = (# of drive gear teeth) X (Tire revolutions per mile)/1000

 

knot plus knot equals knot huh? yea good luck with that .LMAO. Sick

 

Lol now I actually have to take the gears out to find out how many drive gears there are lol. They range from 8 teeth to 18 lol and if there were 8 teeth in there lol i'd need a 32 tooth driven gear lol and the largest one is 25 teeth lol. SO looks like I have to put some larger tires on.

 

I found it easy when I contacted those speedometer guys and told them what I was doing. I dont know how he came across what gear I needed but it was right on!