Just put a new head unit in the truck and put everything back together and now the speedometer is stuck at 0,. All other gauges work perfect. What could this be? Are the cluster grounds hooked to the radio

 

if you had the cluster out id check over the connections. if that dont would your Speed sensor is located on the rear end housing. Take it out ( i think a 10mm bolt) and clean it off. The sensor is magnetic and the metal shavings sometimes interfer with it. If that dont work it may need replaced or check the connections at your fuse box panel on drivers side fender.
I had my speedo quit working and found that the connections to the fuse box came loose. It had previously had the cab off for engine work and they were not connected properly.

 

Did you ever figure out the problem bigred? Today when i turned the key it went to 50mph but moved normally while I was driving. As if 50 was 0

 

I would say rear wheel speed sensor... Is your abs light on? I encountered similar problems.. My speedometer would just all of a sudden fall to 0 while driving down the freeway and then bounce backing nothing was wrong...

 

Abs light never came on. No codes. After a day of driving its back to normal.

 

Most bizarre thing.... Today after reading this post I go to drive my truck and same thing Speedo not working along with my abs light is on I scanned for codes got none for my abs and and only my egr code came on which I am already aware about. If any one knows what the problem is I'd greatly appreciate it.

 

It's your rear wheel speed sensor most likely... Mine is the same way...

 

Yes I fixed it, sorry it took so long to reply, when I installed the new head unit I taped the wires I didn't use together instead of separately so they were grounding off each other causing it not to work,.dip I taped them speratly and it works perfect now!

 

So in my case, abs light on Speedo stuck at 0mph, it's the rear wheel speed sensor and not the tranny speed sensor?

 

Yes. The speed sensor on these truck are located on top of the rear axel housing. Pull it out with a 10mm wrench. clean it off and see if it works. If not replace. They sometimes pick up alot of metal shavings which interfers with it. They dont have a speed sensor on the tranny like other trucks do.