06 w900 speedometer jumping all over

I've just had this problem rectified, my speedo would jump around @100kph, Kenworth found a ground fault in the wiring loom on the motor. (C15)

 

We will run new shielded wiring from the trans speed sensor to the ecm, this has fixed this issue in the past. if the old wiring shorts to ground or some times picks up interference from laying next to oil and air lines it makes the speedo jump as when parked and doing a range shift will do

 

My issue is fixed. I removed the harness, And inspected the wires for chaffing or pinches and found none. I checked the resistance on both wires while jiggling the harness to see if there were any shorts/breaks and found none.
The last two feet of the harness closest to the speed sensor were not a twisted pair like the rest of the harness, so I twisted them. Reinstalled the harness and have not had any issues in the last 700 miles.

 

Im having same problem changed sensor checked wires thight yoke nit, my needle froze over 80 and when the trucks running in neutral the miles keep rolling and im not even driving 3406 e cat 95 kw t600

 

My speedometer was jumping, after reading your answer I checked for play in driveshaft, It was clunking up and down with noticable play. After getting it tightened the vibration went away and speedometer and cruise control work perfectly. Thanks to your post

 

You were right my yoke nut was loose, too much play in driveshaft. After getting it tightened the vibration went away and speedometer and cruise worked perfectly. Thanks for your help.

 

The more and more I work on trucks, the more I use red locktite!

 

Hey man did the yoke nut fix your issue? My truck is doing the same thing. Speedo kept jumping around and getting stuck at 90mph. Once I realized I couldnt change my duty status, I shut the truck off with the needle at 90 mph. But then when I turned the key to restart the truck, the needle went further and is now stuck on the trip reset button. Haven't tired driving yet and don't know if I need to be dropping the drive shaft to try tightening this nut

 

Did u figure this out mine is doing the exact same thing with new speed sensors and speedometer?

 

Did you ever figure this out mine is doing the exact same thing and I’ve replaced sensors and speedometer