Speedo drive gear

[Brownme1988]

2000 Ranger with 235/75/15 wheels/tires. Speedo shows faster than what it actually is.
4.10 gears and a (I believe) 7 tooth drive gear in the auto trans. I think I need to replace the speedo driven gear with a 20 tooth, from a 23 tooth. Can anyone confirm or deny?

 

[sgtsandman]

I can’t confirm the tooth count but I can confirm the indicated speed being about 2 mph faster than the actual speed you you are traveling.

 

[Curious Hound]

2000 Ranger with 235/75/15 wheels/tires. Speedo shows faster than what it actually is.
4.10 gears and a (I believe) 7 tooth drive gear in the auto trans. I think I need to replace the speedo driven gear with a 20 tooth, from a 23 tooth. Can anyone confirm or deny?

A 3 tooth change is a lot. But to help, we need more info. What did you change that is throwing it off? Did you change the differential gears? If so, what was the original ratio? Did you change tire size? If so, what was the original size? This is a mathematical exercise. So you need to compare old data with new data to find out what new speedometer gear is best. You may never get an exact match. 2 or 3 mph error is small enough that you may just have to live with it unless you install a device that electronically changes the signal being sent to the vehicle's computers.

 

[RonD]

Just go here to confirm what you need: https://www.tciauto.com/speedometer-gear-calculator

Yes, it is a 7 tooth drive gear
You need your tire diameter, 235/75/15 is 28.9"

Yes, 20 tooth