Speedometer with a mind of its own

[CinnamonNY]

I noticed the speedometer has a mind of its own, and it decides when it like to work and when it doesn't. I was driving and all of a sudden I look down, and the speedometer reads 50mhp, a few miles later I look down and the needle is dead on 0mph while im driving on the highway. This has happens quite often and sometimes it works the whole ride, sometimes half the trip, and sometimes not at all. I haven't had a chance to really check anything out on it yet, so I was wondering if anyone else has experienced this.
Thanks for any help
Brian

 

[section525]

Brian.. do you notice any other differences in the truck when the speedo isn't working? Such as shifting differently or anything? You speedo is controlled by the VSS [vehicle speed sensor] on your tranny (or tcase if youre 4wd). I'd say either the sensor went bad or possibly its dirty. Otherwise its probably a computer problem which would not be a good thing.

 

[CinnamonNY]

There is not difference in the response or driving. Sometimes when I go over a bump, and its working the needle will jump up and then down to 0mph. Its strange, I think i might have my mechanic look at it.
Thanks

 

[section525]

Sounds like its actually a physical needle problem then. I think you're in the clear. You can find new speedo clusters on eBay dirt cheap too.

 

[CinnamonNY]

I forgot a detail (absent minded sorry), the odometer is staying at the same mileage while the speedometer is not working, so that is what had me worring. I've only had the truck for about 2 weeks now and its been great other than the speedometer going crazy.
Thanks