There are two basic ways to correct a Jeep TJ's speedometer when changing tire sizes. The traditional way is to change a small plastic gear in the transfer case. Cheap and easy to do by all accounts. However, if tire sizes are changed again, the gear must be changed again. So I went with the second way: An electronic lump that recalibrates by connecting in series with the transfer case's speed pulse connector. This can be programmed for whatever offset is needed as often as is needed. A very tiny potted control board remotes to the engine compartment. Zorba's Jeep
Tires
"SpeedoDRD" to re-calibrate speedometer after tire size change.
This is the business end - note programming pushbutton.
Fished up as far as I could get it into the engine compartment. See text.
Plugs in series with the speed pulse output on the transfer case.
Installation was just as easy as the manufacturer, "12 o'Clock labs" claimed it would be. My only gripe is that it would have been nice if the cable had been about a foot longer, it barely reached a quasi-suitable location in the engine compartment. It would have been fantastic if the cable had been about 3 feet longer and the potted control module had been "soft wired" such that it could have been located under the dash in the cab, away from the very high underhood temperatures. But it seems to work fine, the speedometer continues to read correctly as I haven't yet programmed an offset - but now the Jeep is finally ready for some 31 inch tires. I also tested the cruise control which also uses the same signal - it works fine. On to tires!
Stay tuned for tires!
ThinkWare F70 Dash cam, because I'm tired of idiots.
Simple, inexpensive, and no damn smartphone needed.
Power cable routed through windshield escutcheon similar to the GPS cable.
Definitely a Class-A Kludge, but a workable one. Sw. +12 to cigarette
lighter receptacle to splitter to power cords for both GPS and DashCam.
It all tucks up behind the dash to the left, a tye-wrap holds it in place.
F70 Dash cam checkout video.Read on for the next part!
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