Speedometer Pinion Gears

Above are the 31-tooth (#52067631) and 32-tooth (#52067632) short shaft speedometer pinion gears for the '93 and up XJ. I was amazed at the difference in size between the two, as there is only 1 tooth difference between them. I assume that this is the reason why the transfer case next to the gear is marked in ranges of teeth such as "32-38", etc and is indexed by turning the fork that holds it in. I guess that when you use a smaller gear like the 31-tooth, it is offset further towards the ring gear by the fork than the 32-tooth is in order to make contact.

The reason I have both gears is that I was originally going to go with 31" tires with my current 3.55's (planning to regear in a few months), and the chart calls for the 32-tooth gear. I had a hard time locating this gear, as it is on a national backorder that numbers in the hundreds, and paid a pretty penny for it. I then decided today to go with 32" tires, and luckily the local dealership had the 31-tooth gear in stock that this configuration called for.

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

The difference in size is because the gear pitch must remain constant (to made with the speedometer drive gear,) so they have to make allowance for gear size. You are correct - that's why you can index the gear holder in the transfer case.

Let me know if you decide to get rid of the gear you don't use - I'm working on ideas, and I'm collecting a set of speedometer gears for one. I'm not sure if I have either of those offhand - and I'm working on reorganising things, so I'm not sure where my stock of gears on hand happens to be...