With the new gears installed and new tires on the way I need to recallibrate my spedometer. Right now my speedo reads about 65mph when Im actually only gonig arond 45

Where can I pick up a new gear from? Is there a store online that I order from or is this something the dealer would carry?

Dealer or 4 Wheel Drive Hardware

How do I determine what tooth gear I need? I see ranges varying from 31 - 35 tooth

There is a good chart on our site here: http://www.higherground4x4.com/Tech_speedometer_gear.htm

To arrive at a correct Jeep® part number add the tooth count for the speedometer gear to the end of 520676. For a 26 tooth gear the correct part number is: 52067626.

With the chart, we figured out that part number 52067631 was the correct gear for Dana's set up and she was able to pick it up at the dealer for under $20. The difference in gear size is quite apparent, moving down in size from 34 to 31 teeth.

We checked her speed with a GPS for the install too.

The install really only takes about 5 minutes.

I need the 37th tooth gears for 35's with 4.56 part number 52067637 ?

That is correct.

But as a rule of thumb, true tire size and manufacturer listed tire size are not always equal. So it's a good idea to actually measure your tire size (preferrably with new tread).
I know with Dana's, even though we picked the correct gear for her set-up, her speedo actually shows a couple miles below, still keeping her correct speed legal, but still just a hair off.

If you got a set of 35 MTR's then it will be more like 34's. MTR's run small.

Pro-Comps run about a 1/2" small so I was ok.

4 Wheel Parts carries the gears too

My X has no easy speedo fix :cry: