The well known speedometer issues.

[gtmacjr]

Dreaded Speedo Mystery solved

Really this is my first post, but after reading through the forums on this issue and being a maintainer by trade, I couldn't let this Gremlin go any longer in my 2003 Liberty.

What I have found is that the ABS sensor in the rear diff (whether you have ABS or not) is the Speed sensor and was dying after the original lasted over a decade. I replaced it with another MOPAR sensor and it went out after a year. I then bought different brands hoping it was just a bad sensor but had to replace them every year and sometimes only after some months depending on seasons.

After the second sensor I bought the MOPAR wire assembly to replace the connector and wires at the sensor.

After the fourth I did something crazy, you will like this one. I checked the rear springs, which were an inch below spec. Yep, if you have not lifted your KJ and are having this issue it is possibly your springs have sagged over the years, just enough to cut off the air flow at the sensor and it will fry over time. I replaced the rear springs and the fifth sensor has been working ever since.

Hope this helps!

 

[duderz7]

Air flow? Isn't this a wired sensor?

 

[Billwill]

I cannot see how airflow affects the diff sensor. Maybe changing the height of the jeep moved the wires slightly so they are no longer shorting to chassis somewhere.

Saw an interesting post on Lost where a 2005 KJ owner was repeatedly replacing his diff sensor....would run for a while and then fail.

He drained the rear diff oil and found metal flakes in it so unfortunately it seems he has found his problem with the sensors!

 

[gtmacjr]

Air flow? Isn't this a wired sensor?

The Air Flow cools the rear diff, which prevents the temperature from reaching a destructive level. A fact to support my solution is, I have a buddy with the same Liberty, which is lifted. He has never had to change the ABS sensor.