I've been chasing a problem with my speedometer and cruise for a while now. As anyone with this problem knows, when the needle is bouncing, the cruise does the same thing.

I put a new sensor on it - seemed to help for a little while, then back to bouncing speedometer. I replaced the wire from the sensor to the firewall where it all comes together because that wire had some worn spots on it. Again, helped temporarirly, and back to bouncing. Its now intermitten, where the needle will be nice and steady at highway speed, but twitch at anything below about 15MPH, and other times without any reason it'll act up and bounce. However, when its steady, you can set the cruise, and it goes haywire again. So, that leads me to beleive I have some sort of electrical problem somewhere, but I have ZERO electrical experience, and need someone that will feed me some ideas on where to start and how to troubleshoot.

As always, much appreciated.

 

Do a search, There is a disc at your ratio adapter that you should try rotating 10* CCW. It's real simple, it involves loosening a bolt and turn using the ratio adapter as a wrench to turn it.

 

Timmy's correct: a 1/2" cap screw on the tranny holds the speedo driven gear journal in place on the tranny. (My truck is 2WD, yours may be elsewhere). Loosening the cap screw and rotating the journal increases or decreases the driven gear tooth contact onto the worm drive. I found that rotating the journal about 10* CCW stopped my needle bounce and steadied my cruise control. When doing this, push the whole contraption toward the tranny casing to be sure the journal remains well seated in its place. Don't worry if the clamp yoke does not line up with grooves on the journal, just tighten up the cap screw a few lb-ft and road test it. If it's good, you're done. Enjoy!

 

So the fact that the speedometer works correctly somethimes, and when working correctly I can set the cruise and cause it to go haywire is not an indication of an electrical problem?

 

I think the PCM runs that stuff too, so that might be your electrical issue.

 

The problem could be with the speedo drive gear. Drop the drive shaft at the back of the trans. There is a yoke nut holding the yoke to the back of the tranny. Tighten that nut to 280 lbft of torque. The only thing keeping the speedo drive gear from moving is that nut. The drive gear has a spacer on either side of it and is only kept from moving by the pressure supplied by the yoke nut.

Bob