I have 31 inch tires on my truck, it messes with my odometer and speedometer readings, anyone know if there's any way outside of taking it to the shop I can get those synced together with the trucks actual speed and ground covered?

 

got a gps? my tom tom has a speedometer on it. drive with one till you learn your speed.

 

amazing idea!! the only thing that doesn't do is help your trans with the proper shiftpoints, and your ECU with the RPM -> Tire spin mathematics! but stll

 

That's weird. My speedometer is dead on accurate with 31s, it was off with 235/75s.

 

What year is your truck, the guy with the gps is taking the cheating way and seems to be to lazy to fix it correctly. Before 92 the best bet is to find a mechanical speedometer corrector because the factory gears are getting hard to find. For 92 and later you can reprogram your speedometer fairly easily without going to the shop. There are instructions listed in a previous thread about the procedure and also has some of the numbers for common tires.

 

jeez rude! am I lazy? no, my tires are back to stock size now and my speedo works fine. I'm just giving a cheep and quick way to not get pulled over or photo tickets.

 

She's a 1990. Any ideas on where to get one, how much they cost, and knowledge to if they work?

 

change the gear on the tranny side of the speedo, call a tranny shop with your stock tire size, tranny code or type, current tire size, and rear end ratio. they will tell you what tooth gear you need, i think lmctruck.com carries different tooth gears.

 

The gears are on the VSS (where the speedo cable connects to the transmission). You'll need to change both gears to keep them from chewing each other up.

This site will give you some good info on how to find the correct gear ratio:

http://bronco.zenseeker.net/Speedo.htm