Speedo Drive Gear Teeth

Anyone know how many teeth the speedometer drive gear has? I have a formula to figure out what driven gear I will need, but I need to know the drive gear tooth number to use it. I found a chart for what driven gear to use for tire size vs. axle ratio, but it doesn't go down to 3.55's.

I have a 92 auto w/ NP231 t-case


Thanks.


woops, I found this (is it correct?): http://www.high-impact.net/transmission_and_gear/DodgeSpeedoGears.htm
I also found this and it's different: http://www.gotjeep.net/speedo.html

I had 3.55s from the factory I believe I had a 27 in mine

I have 4.88s and 35s and had to go to a 39 tooth to get it straight

My dealer had a full printout of exactly what I needed

I used this chart.

Compliments of GoJeep!

http://www.go.jeep-xj.info/HowtoSpeedoGears.htm

Thanks.

Hmm, seems like every chart I see is different. I guess I will just do the 10 mile milemarker test to see what % it's off and go from there, then.

If I am figuring this out correctly, for a 29-tooth driven gear to be needed w/ 3.55 gears and 32" tires, the drive gear would have to have somewhere between 12 and 13 teeth.

I have a gps that tells me how fast I'm going.

Changing the gear seems like alot of work when you will probably want to change tire size again in the future.

changing the driven gear is easy. I wouldn't have to change the driven gear, which is a little bit of a pain. These are only temporary tires, though.