I’ve got a 97 f150 that came with 235/70/16 tires. I plan to put on a set of 265/70/17 tires on, and am trying to figure out what speedometer gear I need to put in. Going by the tire height, I’ve found that there is roughly a 10% difference in circumference, which is what I assume to be the amount that the speedometer would be off. I equate that to needing a driven gear with about 2 less teeth. I pulled out the gear that’s in there and unless I counted wrong a dozen times, it’s a grey gear with 22 teeth. I looked all over and found no trace of a 22 tooth gear existing. Does anyone know of that? And does anyone have an idea as to where I can get a 20 tooth gear?

 

If you have 355 gears, then the closest you can get is an 18 tooth. White should be the color. I forgot that the F series uses an 8-tooth inner gear.

You can use this link to verify, in case you have a different rear axle ratio.

https://lmr.com/products/Mustang-Spe...ear-Calculator

 

I found that a good place to get the speedometer gear you need is on ebay. They usually have someone selling them for not a lot of money (about $12.00). I had to change mine because it looked fine but it was worn out where the cable goes into the gear. I then had to change it again when I bought bigger tires. We have a speed indicator in my town that tells you how fast you are going and I checked my speedometer against that and I was dead on. I believe that I have a 20 tooth gear but I can't remember the color since I did this a few years ago. You can also check with Rock Auto to see if they have the part you need.