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Speedo gear Question

truck7575

truck7575

NAXJA Forum User
Location
georgetown
I have been looking at replacing my speedometer gear and I have 32 inch tires and 4.56 gears but I have found three different sources that say i need three gear numbers of gear teeth. Whats up with this? is there a set in stone way to figure it out? Should I go by the size on the tire itself or fill it up and measure how tall or what? Can anyone help?
 
I'd probably go with a 40 as recommended by gojeeps' chart. Another option would be to compare your speedo to a GPS, figure out the percentage of error, and buy the appropriate speedo gear to correct it.

Keep in mind though that your percentage of error will continue to change as your tires wear. According to gojeeps' chart, your gears with 32's should need a 40. After wearing 1/2" of tread off your tires you would have the same diameter tire as a brand new 31. This new size would require a 42 tooth speedo gear. Moral of the story is that unless you're always going to have fresh tires on your Jeep, close is as good as you're going to get.
 
To add to what fyrfytr1717 said the gojeeps chart said I needed a 37 tooth gear. (4.10s and 31s) After my regear and checking with my GPS and doing the math I found I needed a 37 tooth gear. (Surprise!) Speedo is within 1 MPH with new 31 inch KM2s. Just be advised gojeeps charts are based on BF Goodrich tires. Other brands may be a different size. In my experience, BFG tires are close to the stated tires size other brands may be smaller.
 
bwinter1946 said:
To add to what fyrfytr1717 said the gojeeps chart said I needed a 37 tooth gear. (4.10s and 31s) After my regear and checking with my GPS and doing the math I found I needed a 37 tooth gear. (Surprise!) Speedo is within 1 MPH with new 31 inch KM2s. Just be advised gojeeps charts are based on BF Goodrich tires. Other brands may be a different size. In my experience, BFG tires are close to the stated tires size other brands may be smaller.
Click to expand...

That's because speedos are set up to read high. The odo is different and should be really accurate with stock tires
 
I found the speedo gear that you need.

 
Advanced Adapters and another site both said I need a 37 tooth gear.. Also I have 32x11.50x15 BFG KM2 tires and they seem to be smaller than other 32 inch tires plus doesnt it actually matter how much air is in your tire and isnt it the circumference of the tire and not the diameter that matters since the distance of the edge of a circle is the distance around the circle and not from one edge to another. Whatchall think?
 
I've got 4.56's with 32's as well, and wound up with a 40 tooth speedo gear. At 60 mph, I register 61 mph on my gps....close enough for me.
 
remeasured tires they are 32" right on, advanced adapters is sending me a 37 tooth I wonder if I should send it back or keep it for when I upgrade to 35" tires and just order another 40 tooth for now.
 
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