My 77 f250 has a set of 37" Toyo m/t's on it and the speedo is off at higher speeds. I was wondering if I got my speedometer re geared if it will fix this problem.

 

That will fix your problem. Most cities will have a shop that does recalibration. Check a few driveline shops.

 

No need to waste your time with a shop. You just need to change the driven gear on the end of your speedo cable where it installs in the trans. It takes about a minute and a half and you can buy the gear for about $15. A gear with less teeth will drive the speedo faster which is what you need with taller tires.

 

I've used this calculator to select the right gear. Remember,you're looking for the driven gear. Leave the speedo revs per mile at 1000 and enter 7 for the drive gear teeth. You also need to know your rear gear ratio. The result will tell you which driven gear you need.


http://www.wallaceracing.com/speedo-calculator.php

Here's what the gear should look like. Make sure to get one with the proper tooth pitch. There are both right and left handed versions but they are marked as in the photo.


<a href="http://s742.photobucket.com/user/Fordworth/media/Seedo%20gears/2013-01-02_19-50-47_578_zps5ab65cdb.jpg.html" target="_blank"><img src="http://i742.photobucket.com/albums/xx65/Fordworth/Seedo%20gears/2013-01-02_19-50-47_578_zps5ab65cdb.jpg" border="0" alt=" photo 2013-01-02_19-50-47_578_zps5ab65cdb.jpg"/></a>

 

So I just used the calculator and it says I need 15 gears, does that sound right to you

 

That very well may be right. However, they only come with as few as a 16 tooth count.

 

What is your rear gear ratio?

 

The tag on the diff says 4:10's

 

Bronco graveyard has them