i saw a few months ago where somebody was wanting to use one of these but was not sure on how to set it up. i have since installed one on my TJ and would like to share how to do this. if you have a gear driven speed-o-meter this doesn't pertain to you. however if you have a tone wheel in your t-case, like that of a Rubicon or on some after market SS SYE kits, than this may be of some help.
so in your tone-wheeled jeep with larger tires and different diff gears this is important so you know how fast or slow you are going and how many miles you are racking up. you do have other options like the thing from superlift (about 200) or that other thing that somebody else makes (also about 200). or you can buy the SGI-5 from Dakota Digital for about $80 from places like Summit.
with all that said and done it is time for the install.
1) pick a good location to mount the box. you will want some place that is safe from attack by water and other elements but that is also easily accessible to adjust the calibration at a moments notice. i used the side of my glove box right next to the dash speaker.
2) find a place to tap 12V+ when the key is in the on position. this will go in the cleverly named "power" port
3) find a good ground for the unit. this wire shall go in the "ground" port
4) run the wires for your input and output terminals. i found using a hunk of good ole speaker wire was a wise choice as there needs to be a wire going from, and to the speed sensor and this just keeps the wire running to a minimal.
5) this is the no turning back point. cut the signal wire (i chose to cut it on the vehicle side of the wiring harness) and leave enough room for a butt connector on each side of the cut (the signal wire on my application was the tan/brown wire. this may not be true for all sensors).
strip both ends of the wire and get them ready for the butt connector. now take one side of the speaker wire from step 4 and splice it to the pre stripped end of the signal wire. take the other side of the speaker wire and splice it to the other pre-stripped end of the signal wire hanging from the jeep. basically what we have done here is add a long piece of wire to the signal wire. NOTE: you will want to know which side of the speaker wire is attached to the sensor, and which side is attached to the computer.
6) go back to the SGI module and attach the wires. you will want to use input for the piece of wire attached to the sensor. and for the wire connected to the computer side, use output 3. NOTE: this should hold true to all jeeps and Chrysler vehicles but dont hold me to that.
7) set the 4 small white switches
switch 1 on
switch 2 off
switch 3 on
switch 4 off
8) installation is complete. time to make sure you didn't screw anything up
start the jeep and drive it. if the little green light blinks as you roll all is well. this means the signal is running through the little black box and back out to the jeep. another good sign is the speedometer is giving feedback.
if all is well it is time to calibrate the do-hickey. do this however you like as long as it is safe. the tried and true grab your closest friend with GPS and can follow directions and communicate properly seams to work for me. please be aware that there is some lag between the GPS and the speedometer. it is probable best to do the calibration on long flat roads with no stops.
mash the up and down buttons accordingly until the display reads the correct speed. i think that should cover it. happy jeepin!