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ajohnson928 12-31-2008 04:56 PM

Speedo went crazy...
I've got a 97 TJ 2.5L 5spd with 112K on it.

The other morning while I was driving about 45mph the speedometer started jumping up to 55-60 then dropping down to 30-35. When I got home I parked her and let her sit most of the day. That night I drove it again and there was no problem for several hours then it began again. Eventually it was dropping lower and lower (saying I was going 35 on the interstate when I was doing 65-70). Eventually it just stopped working all together.

Later the Check Engine light came on. Pulled to code (0500 malfunctioning speed sensor) and then changed the VSS. Cleared the code but nothing happened with the speedo with the new VSS. The odometer is not clicking miles over but the shift light has worked all along.

I pulled to cluster and checked all the connections. No change after that. I'm stumped ... anyone else know what's going on?

distortedtj 12-31-2008 05:02 PM

Your shift light works off of RPM's

Look at the backside of the transfer case. Where your speedo gear is located. Check the electric connector going to it.

distortedtj 12-31-2008 05:03 PM

ajohnson928 12-31-2008 05:08 PM

I just ran out and checked it. It's tight.

The connector was replaced with the VSS.

Any other suggestions?

ajohnson928 12-31-2008 05:09 PM

oh and the shift light is coming on even in 5th gear.

Jerry Bransford 12-31-2008 05:19 PM

What do you mean the connector was replaced with the VSS? If you still have a speedometer gear, which you would unless you have a super-short JB SYE kit installed, it's probably just not fully engaging the pinion gear inside. To cure that, you need to rotate the speedometer gear housing a tad to get it to fully engage again. But if its been doing it long, the plastic speedometer gear teeth may be worn so it may need replacing.

distortedtj 12-31-2008 05:36 PM

To piggyback on Jerry. To pull the speedo gear out just take the bolt with the retaining clip off to remove the speedo assembly. The speedo gear will be attached to it and will come out with the assembly. Inspect it closely for any damaged or missing teeth.

distortedtj 12-31-2008 05:41 PM


Originally Posted by ajohnson928 (Post 301159)
oh and the shift light is coming on even in 5th gear.

Even though the arrow points up, It also tries to work as a downshift light also. It's the computer wanting to keep within a certain RPM for "jeeps" so called maximun fuel saving range.

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