I posted this in another thread but this is what helped me....
If you have just replaced your speedo gear and now your speedo isn't working, this very well may fix your problem. For those of you who have just installed a SYE, you will want to see the pix at the bottom of this write up.
Now for you guys who have the stock Transfercase (TC) and you just change your speedo gear because you either changed your gearing or put on larger tires, you may have reinstalled your speedometer off calibration.
On your TC, there will be a little nipple or hump
Now look on your sending unit (speedo) and you will find two sets of numbers. 26-31 and 32 -36. These are your calibration number that you will use to line up on the "nipple". Your new gear will be in the set of numbers on the unit. If you installed a 34 tooth gear, then you would line up the 32-36 set of numbers.
Now install the sending unit into the TC being sure to line up the numbers that apply to the gear you installed with the nipple. You may have to tweak the unit a little for the hold down clamp to line up. What is important is that the numbers are within proxemity of the nipple.
And thats it. really pretty simple. Fasten down the hold down clapm and you are good to go. If yout speedo still doesnt work, then very possibly you may have a bad unit or the electrical contacts are dirty.
Now for you SYE guys/gals...there is NO NIPPLE or hump on the tail houseing of the SYE. What you do is you line up the correct speedo numbers with the clamp.
Real simple..Hope this helps.