# Truck speedometer issue?



## #1DEER 1-I (Sep 10, 2007)

Hey guys I have a mechanical question. My 05 Silverados speedometer isn’t working properly. It is reading under the speed I’m going, it seems like by about 15-25 mph under what I’m actually going. The speedometer kind of slides in a jerky motion instead of a smooth motion like it used to. At times it seems like it reads correctly, but there are other times it defiently is not reading correctly. What would be the issue here? The speedometer motor itself? Or the speed sensor on the transmission? Thanks for any help.


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## Critter (Mar 20, 2010)

A lot of the vehicles out there now days have the speed sensor on the rear end and over time it will get gunked up where it starts to cause problems. Also they are no longer mechanical with a cable running up to the speedometer but electronic where a bad sensor can cause you problems.


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## DallanC (Jan 13, 2009)

Its a known issue. The servo's go bad in the dash cluster. If you can solder connections, its easy to buy a bunch and replace them all on a lazy sunday afternoon.

https://www.amazon.com/Instrument-Dashboard-Silverado-Cavalier-Avalanche/dp/B004PXAUGC

-DallanC


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## #1DEER 1-I (Sep 10, 2007)

Critter said:


> A lot of the vehicles out there now days have the speed sensor on the rear end and over time it will get gunked up where it starts to cause problems. Also they are no longer mechanical with a cable running up to the speedometer but electronic where a bad sensor can cause you problems.


Hardly recognized your profile with your updated picture critter. I appreciate it. My truck is not a cable, it has the sensor you speak up towards the back side of the transmission with a widening harness running to it. It isn't too hard to get to, I guess I could replace it and see where it takes me. The speedometer still works it just isn't reading the right speed and isn't as smooth moving around. It also sits below zero when at a stop or the truck is off. I'm pretty certain it sat right on the zero before.


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## ZEKESMAN (Sep 14, 2007)

#1DEER 1-I said:


> Hardly recognized your profile with your updated picture critter. I appreciate it. My truck is not a cable, it has the sensor you speak up towards the back side of the transmission with a widening harness running to it. It isn't too hard to get to, I guess I could replace it and see where it takes me. The speedometer still works it just isn't reading the right speed and isn't as smooth moving around. It also sits below zero when at a stop or the truck is off. I'm pretty certain it sat right on the zero before.


if your speed sensor was failing you would have a check engine light on


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## #1DEER 1-I (Sep 10, 2007)

ZEKESMAN said:


> if your speed sensor was failing you would have a check engine light on


The check engine light does come on from time to time, and then turns off usually before I have time to go read the codes on it. It's off right now, but it came on yesterday when I was on the mountain and went off before I got down.


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## DallanC (Jan 13, 2009)

Codes are stored, so even if the light goes back off you can still read it. I keep a cheap code reader in my console and check / clear them out from time to time. I only worry about a code if it keeps coming back repeatedly after a month or so.


-DallanC


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