speedometer gear

[olemech]

i have a 1996 explorer4x4 and i will be puting 30x9.50 15s on it and i need to know what speedometer gear to put into the trans to keep the speedometer reading right. thanks for any help you give me. phillip allen pallen5@juno.com:yelexp:

 

[Alec]

I'm assuming now you have 235/75 tires. From them to the 30's won't be much difference, so you might not be able to correct for that. However, you'd need to take out your current gear and count the teeth and possibly go one step lower.

 

[Robert]

Each step up or down in gear teeth amounts to approximately 5%. If you are going from 29" (235 75/15) tires to 30" tires you are changing your overall ratio by almost 4%. You would be closer if you got the new gear with one less tooth. The only way to know what gear to get though is by counting the teeth on your current gear and knowing the diameter of your original tires and your new tires.

 

[Alec]

But remember, a standard size tire is almost never the size it says it is. For example, a 31 is usually about 30.7". Just keep that in mind, you might need to go to the manufactureres website, or tirerack.com to find the exact measurement.