Speedometer just started bouncing around erratically

KCsTJ said:
Yes it is at that location. So far, since I found and taped those two exposed wires, no more Speedo needle jumps.
Glad you found yours fixed.
Mine is a daily driver too
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Back to square 1. Speedo needle going nuts, seems almost every time it shifts from 1st to 2nd. Ugh....
Edit: was fine till Eagle Transmission in Mckinney, Tx did an overhaul last week on my 32rh 3 speed auto, ugh time to recheck stuff
I hate when a professional shop screws up my jeep :-/
 
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FIXED !!! Problem resolved..... after reading the FSM about the VSS I decided to clean the 3 pins in the VSS connector at the transfer case.
I took a Q tip with cleaning solvent and cleaned around the connector pins, which did not look dirty at all
Lo and behold, I reconnect the VSS connector, went for a test drive and NO MORE SPEEDO NEEDLE JUMPING. Yay!
 
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I am in the same boat my needle is going all over the place and around the world. Just another thing.
 
Jon Wildes said:
I am in the same boat my needle is going all over the place and around the world. Just another thing.
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Check to see if the wires around the transfer case and transmission have the protective loom.
Zip tie the wires securely.
Wires flapping around the tranny, tossed around by driving will cause Speedo needle bounce.
 
Older thread that Ive contributed to already but good info. Mine was going crazy for a bit, I jostled the VSS plug and the speedo at least quit wrapping itself around to the trip reset button. I think I have a bad ground somewhere. Mine tends to drop in speed when I give it gas. It has also been reading anywhere from 15mph to 40 mph off.
 
tworley said:
Older thread that Ive contributed to already but good info. Mine was going crazy for a bit, I jostled the VSS plug and the speedo at least quit wrapping itself around to the trip reset button. I think I have a bad ground somewhere. Mine tends to drop in speed when I give it gas. It has also been reading anywhere from 15mph to 40 mph off.
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i pulled the plugged and cleaned it with contact cleaner and its working fine so far.
 
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I know this is an old thread but... I was experiencing the same problem. I did all the typical things to diagnose such as 1) Cleaned sensor plug and wires. 2)Replaced speed sensor. 3) Checked Voltages at plug. 4) Checked ground at engine block. 5) Checked plugs on the back of the cluster and did cluster diagnosis. Nothing solved the problem.

But then I noticed the battery was loose so I decided to tighten the hold-down. That's when I noticed that the bolt on the back of the battery hold down was up against the gray plug that goes into the PCM. The loose battery allowed the bolt to wear-down then chaff one wire in the cable group. White with an orange stripe. Just so happens that wire is the VSS signal wire for the PCM. It was occasionally being ground when I hit bumps, when around corners, etc. Basically as the battery shifted around.

Once I cleared that issue up all speedometer problems went away. So be sure to check that as well.
 
Anyone know how to test for a faulty speed sensor?

I've got a very intermittent issue where speedometer drops to zero and all other gauges seem ok.

I have a speedohealer installed as well.
 
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tworley said:
Have you tried tightening the nut on the output shaft of the tcase? IIRC its around 220 ft/lbs. The rubi uses a tone ring and hall sensor. If the ring is loose it will give erratic readings
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I have a YJ with an extreme short shaft conversion and I just wanted to thank you for this suggestion because I’ve been chasing this problem for a little over a month and was never going to figure out it was a loose yoke nut. Tightened it up and my Speedo works again! Thank you so much!
 
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KC97 said:
I have a YJ with an extreme short shaft conversion and I just wanted to thank you for this suggestion because I’ve been chasing this problem for a little over a month and was never going to figure out it was a loose yoke nut. Tightened it up and my Speedo works again! Thank you so much!
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Glad you were able to fix it!
 
Resurrecting this post...

Having erratic tach and speedo needles. They don't bounce around like others have noted, they simply park at zero for a few seconds and then get back in the game, like nothing is wrong. All other gauges work. Jeep runs fine. I do get an airbag light and CEL, but nothing else. If I wasn't looking at the cluster I wouldn't know there was an issue.

Before I start chasing potential issues... Any suggestions?
 
I still haven't located my VSS issue. I've ruled out the speedohealer. I've checked GND and 5V and but my issue is intermittent. Thought about replacing the sensor but I'd like to diagnose it to be the problem. Annoying issue for now. It doesn't throw any codes.
 
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KCsTJ said:
Not to hijack but my Speedo needle started this same erratic movement last week, very intermittent.
No codes.
I'll be following this thread closely
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KCsTJ said:
I'm having the same issue with my wife jeep runs an shifts great no codes did you find you issue with the speedometer bouncing around 2004 Jeep Grand Cherokee Laredo 4.0 4x4 no cable
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Changed speed sensor in tail shaft of transmission I know it's hot to be
Something simple
Help please God Bless You 🙏
 
Godschild2229 said:
Changed speed sensor in tail shaft of transmission I know it's hot to be
Something simple
Help please God Bless You 🙏
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Check all your engine bay grounds
And make sure your battery connections are tight and cables don't bounce around
All your Grounds in Engine Bay need to shine take one at a time and clean them firewall and block grounds I did this an my wife's Jeep speedometer works as it should
 
Sudo said:
New sensor Fix your issue?

I just got done putting in new sensor since I couldn't find any other culprits.
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Just reporting back that it has now been over a month and I haven't had any speedometer issues. Problem has been resolved.
 
Has anyone experienced their automatic transmission suddenly feeling like its disengaging and re engaging when their speedometer starts jumping around?
 
Paul_G said:
Has anyone experienced their automatic transmission suddenly feeling like its disengaging and re engaging when their speedometer starts jumping around?
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Can't help you with this one. The erratic speedo issue was loose ground to the block. I have a 5 speed so can't offer any insight on an auto.
 
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