speedo gear with jb supershort sye

[dae03TJ]

i have a jb super short sye and i remember reading something about it being electronically adjusted for speedometer. i have 4.88 gears with 35" tires and the speedo is 10% off. is any one else running this set up and if so what did you do to fix it.
according to a site i found http://www.go.jeep-xj.info/HowtoSpeedoGears.htm
i need a 39 speedo gear.
the site i found to order
http://www.transmissioncenter.org/speedometer_gears_for_dodge_and_jeep.htm
doesn't carry a 39 its either 38 or 40. sorry for the length any help would be appreciated.

 

[crgrissom]

Your SYE does not use a speedo gear, so you can't go by that chart. See this writeup:
http://www.rockcrawler.com/techreports/jb_short_sye/index.asp
It says:
"Dakota Digital SGI-5 Universal Signal Interface which:
* Allows adjustment of the electronic signal from the new speedometer sensor to accurately calibrate the speedometer.
* Allows use of different-sized tires or gear ratios down the road with no additional investment
For many people, the Dakota Digital device may not be needed as JB Conversion has setup their electronic control in a range that emulates the "factory" and will provide an accurate reading to your speedometer if you are using a tire and gear combination that is close to a 4.10 and 31" such as the stock configuration of a Jeep Rubicon. For example, if you are running a true 35" tire and 4.56 axle gears which are pretty common on YJ's and TJ's these days, you probably won't need the Dakota Digital SGI-5. I opted for the SGI-5 because I run two sets of tires and would really like the ability to flip a couple of switches when I change tires and know that my speedometer is still accurate."

Chuck