How to I correct my TJ's speedo?

[TerryMason]

I've put 33s on my TJ, and would now like to correct my speedo. I did this in my CJ by just replacing a mechanical gear - is this still the case for TJs, or do I need to reprogram my computer?

 

[jps4jeep]

no, you need to change it in the computer. there are a number of brands to do this, edge, superlift, banks etc.

 

[TerryMason]

Are you sure? I was getting ready to buy this:
30910631 - 31 Tooth Speedometer Gear for 93-06 Jeep® Vehicles - Quadratec

 

[SteelHeadz]

I'd go with electronically correcting the calibration rather than mechanically. If later on down the road you decide to change to a different size tire, all you would have to do is re-calibrate it with the module. I've used the "Jet Performance" calibration kit on a TJ before and it seems to work well.

 

[TerryMason]

I've done a bit of research, and I get mainly conflicting stories. I've read that normal TJs require a mechanical correction (new gear), and that rubicons require electronic calibration, since they don't have speedo gears.

I've found a few electronic options to correct this. I'm leaning towards the SpeedoHealer if anyone has any experience. The Jet tuner looks nice, but is probably overkill for what I want. Skinny Pedal has one that looks nice too.

SpeedoHealer - $160
Superlift TruSpeed - $220
Jet Performance Programmer - $340
Flashpaq Tuner by Superchips - $340
Yellow Box - $110

 

[Bounty__Hunter]

If you want to go with an adjustable box, get the Dakota Digital unit for around $80. I run one due to the super short SYE having the Rubi speed sending unit.

Your TJ has a mechanical speedo gear and is easily changed if you decide to go that route.

I've got a bunch of speedo gears here but the closest I have to what you need is a 30t.

 

[JPNinPA]

I've put 33s on my TJ, and would now like to correct my speedo. I did this in my CJ by just replacing a mechanical gear - is this still the case for TJs, or do I need to reprogram my computer?

Yes Change the speedo gear unless you have a rubicon without the gear. It is easy. Just be sure to adjust it approperately when installing. Read directions for ligning up the connector. Teeth too deep will wear out the gear. Too loose and broken skipping teeth.

PS Changed mine some time ago. odometer and speed are exact using mile markers over 500 mi trips.

 

[QuadRep]

I would change the speedo gear. It wont be spot on but damn close

 

[ademondad666]

there are four indentations on the speedo sensor, if i bought a new gear, put it in and twist the sensor to where it works, is the marks on the sensor accurate to where the braket holds it, not being to loose or tight?

 

[Bounty__Hunter]

There are 3 gear ranges on the speed sensor, and in a few of those positions the clamp will fit into the indentations. Not sure it fits in every range position.

 

[JPNinPA]

Stu's write-up

 

[TerryMason]

For anyone who's interested I've done a writeup on how to replace your speedometer gear. It was much easier than I had expected:

http://www.jeepz.com/forum/drivetrain/32833-jeep-speedometer-gear-change.html

 

[JPNinPA]

This morning I noticed my speedometer read thru the range of 0 to 40 mph and I didn't even leave my driveway. Hummmmmm I wonder if the slippery stuff had anything to do with that.

Nice write up. May want to note or warn, overly state if you don't set the gears correctly they will grind or slip. This will end up in damaging the gear and then no mph reading.

 

[TurboDave]

I have a 2003 TJ with 3.73 gears. I put a 4" lift and 32" tires when I bought it. The result was the speedometer read about 10% slow. I don't know about Rubicon's but I don't think the ECU in TJ's in this period are smart enough to change the speedo. You can fix this problem by ordering a replacement gear for your axle ratio and tire size from Quadratec. It is about a 10 minute job. One screw out on the transmission tail shaft where the speedo connects, pull the original out and stick in the new one, put the screw back and connect the cable and your speedometer will read correct.

 

[jfrabat]

takes under 10 minutes if you know what you are doing... Take out one bolt, take out the main unit, swap gears (simply pull it and push the new one in), insert unit (make sure to use correct range when lining it up), re-inser the one bolt. You are done. I prefer the mechanical ones if you can get them...