dana 300 speedometer gear

Call the Jeep dealer - he almost certainly has a chart for the ring/pinion gear ratio and tire sizes - the FSM for the MJ has a full page chart.

The other way is to simply figure the actual speed (measured mile, GPS, known accurate speedo in another car). Take the indicated speed read on the test, divide it by the actual speed then multiply the number of teeth on the gear you have now by that number. Don't expect perfection - remember that even tread wear causes the accuracy to change during the life of the tires.

On my CJ I have 33" Tires with 4.11 gears (neither of which came with the Jeep). That really put the whammy on my speedo's accuracy. I went to my local speedo shop, they attached some magic box to the back of my speedometer and it calculated the ratio for the converter box they built for me. It cost about $120 as I recall. They certified it as 100% accurate (whatever that means). I can barely read the difference between 40 and 45 MPH on my speedo. But hey, I have a certificate that says it's certified. Yipeeee.

*lol* I refused to have gps I like getting lost in my Jeep.

the dealership here, well they don't seem to have any documentation about anything older than 10 years. (I asked for head bolts for my CJ once, that's how I found out). I might try the 'other car' method

right now I'm using the '40 feels like 50' method

Ron

really? you get a certificate? I live in the midwest now, I don't think there's a speed. shop around here (I don't know of one) I heard the converter boxes are more expensive

Try this

and part #s there's always a post somewhere about where to get Dana 300 speedo gears, so here's a list of DC part numbers.

Teeth Color Part Number

24 WHITE 3410024 25 BLUE 3410025 26 RED 2538926 27 WHITE 52068149 28 BLUE 52068150 29 BLACK 52068151 30 YELLOW 52068152 31 GREEN 52068153 32 BLACK 52068154 33 YELLOW 52068155 34 GREEN 52068156 35 ORANGE 52068157 36 RED 52068158 37 WHITE 52068159 38 BLUE 52068060 39 GREEN 52068061 40 ORANGE 52068062 41 RED 2538941 42 WHITE 2538942 43 BLUE 2538943

I did this Google search: dana 300 speedometer gear chart and found these two useful links on the first page.

That oughta get you started. TrailMarker.

You can use mile markers on the highway and any watch with a secondhand to calculate your speed.

Drive at any convenient steady speed while counting the mile markers. Your true speed is just a simple calculation away.

FWIW: Jeeps speedometers are notorious for their reading fast. Over sized tires lead to increased accuracy.