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NP 231 Speedometer Gear Install Writeup

WB9YZU

NAXJA Forum User
Location
Madison, WI
Let me start with mentioning a couple of items:
* The vehicle here is not an XJ, it is an 06LJ, BUT everything here is the same as a 97 though 01 XJ (well... except for that nice damper in the picture ;) ).
* This procedure is the same as any other Cherokee, except for the electrical connection on some units and that the gear may be a long shaft (year differences).
* There are 2 style gears, long and short. Long gears go on pre-97 units, short go in 97 and up units. You can find these charts very helpful.
http://www.quadratec.com/jeep_knowledgebase/article-46.htm
* GoJeep also has a writeup on this, and I would be amiss not to mention it as he has a lot of info in there.
http://go.jeep-xj.info/HowtoSpeedoGears.htm

I selected the gear for my unit based on gearing (3.73) and tire size (33").
I found that the correct gear was $75 and the gear for the 32" tire was $41. Since the accuracy is +/- 3%, I figured the cheaper gear would work fine.

You will need these items:
* 13mm Wrench
* Vaseline
* Cleaner ( I used a General Purpose house hold cleaner)
* Paper towels
* 15 minutes

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I parked my Jeep with the nose pointed down hill to avoid spilling any fluid. Set the parking brake, and put it in reverse gear (manual) or "Park) (auto). If you have a wheel chock, it wouldn't be out of line to throw it under the downhill side of a tire.

Here is our objective:

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Remove the electrical connection if you want, but it is not necessary if you don't pull the unit to take pictures ;) See the Red slider on the connector, slide it to the right, press on the connector just above the slider and remove. Remove this 13mm Bolt, and only this bolt. Take the bolt and fork and set it aside. Note which slots the fork ends sat in.

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Remove the sensor from the transfer case by rotating CCW and pulling on the assembly. Then pull out the old speedometer gear. It may put up a fight, but there are no clips or anything to remove, so just pull it out.

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Take your new gear, lubricate the gear's shaft with the Vaseline, put some on the gear tooth surface and push the new gear into the assembly while twisting slightly to line up the drive splines inside the sensor with the gear.

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Lubricate the "O" ring with some Vaseline and take the completed assembly and put put it back in the transfer case by offsetting the sensor CCW from it's previous position, pressing and turning. Make sure it seats completely.

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Now rotate the sensor clockwise to the nearest set of marks before the sensor puts up much resistance to you rotating it. This is a soft gear, and you can easily damage it. In this case, the gear lined up close to it's original position.

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Put the Fork back on so that the tangs drop into the slots in the sensor, install the retaining bolt, and tighten. If you removed the electrical connection, put it back on at this point and slide the red retainer to the left until it locks.

Take it for a ride!
For me anyways, the speedometer came out within a mile/hour at 60mph. Since the error showed slightly more on the speedometer than the GPS, I called it good :D
 
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