Speedometer Gear

[1996xlt]

After a bit of searching, (and little avail) I need to know which speedometer gear I need to get my truck closer to showing me a true MPH reading. My truck specs: 96 XLT, 4x4, auto, and electronic shift BW 4404 transfer case, with tow package (LS 3.73). I switched from 235s to 31x10.5 and at 60 MPH I'm actually doing 66. Which tooth count/color gear do I need? TIA.

 

[BrooklynBay]

Check my sticky thread on speedometer gears in the transmission section. It's # 3 in my list of useful threads: http://www.explorerforum.com/forums/showthread.php?t=158739

 

[1996xlt]

(Current Teeth x Speedo Reading)/Actual Speed =17.61 teeth
(Drive Gear Teeth x Axle Ratio x Tire Rev. Per Mile) / 1000 =20.14 teeth

Using these two formulas I get two different answers (see above) from what I've seen from your thread if the speedometer is running fast (+10mph in that thread) you would need a gear with more teeth. So in my case the speedometer is running slow; shows 60 MPH actual is 64.7x (just had it calibrated) wouldn't I need a gear with less teeth?

Edit: Correction its 66.1x MPH(actual) at 60MPH(as read from speedometer.)

 

[1996xlt]

Anybody have any insight?

 

[beachn974door]

Cletus,cletus,cletus......do you not know who to call when you need help on your truck? I have gears in my toolbox at work that I can ship you. Call me

 

[1996xlt]

Ok my tire diameter is 92 3/16, actual tire size is 30.5'' I can't find the formula for revs per mile; help math sucks.

 

[beachn974door]

You need a 18 tooth driven gear. I think I have one I'll check tomorrow