speedo is acting funny
 

the truck in my sig is having issues with the speedo, when the truck is running the speedo will start to sweep, sometimes only a little and other times all the way up till it pegs out then back to whatever speed i am going. it doesnt seem to matter what speed i am going sometimes it does it when i'm not moving at all. is this a sign of bad things to come? or is this a connection issue? where does the speedo plug into the driveline? thanks

anyone know where the speedo plugs into the driveline?

On a 4wd it plugs into the transfer case.
Sounds more like you have a bad connection rather than a bad sensor.

I think on 98 and above it connects to the rear axle. Thats how it is on my truck, the 97 and older are at the transfer case/transmission depending whether you have 4x4 or not.

thanks for the replies. i'll check it out today.

You're right, half way.
On a '98 the rear sensor measures under 30 mph. Above that it's the transfer case or tranny sensor.

It could be a failing diff sensor or the sensor may have some iron dust accumulated on the magnet.