speedometer acting funny

[airgeirb]

Wanted to see if anyone has come across this in the past. My speedometer over the weekend started to jump sporadically. Like i will be going 75 down the freeway and it will jump from 40 to 60 to 30 to 50 you get the picture. It will never stay at 75 just sit there and dance. The shift light will also flash and the brake light comes on when the shift light does. Any help is appreciated.

[moogvo]

Tell us a little more about your vehicle... What year, what is it? From what you are saying, it sounds like you have a bad ground.

[airgeirb]

truck is a 1993 chevy half ton 4wd with 350 and nv4500 manual trans

[moogvo]

WOW! A 1/2 ton with an NV4500! That is awesome! I am sticking with a ground at the moment.

[airgeirb]

yup it has a nv4500, I believe its original. I have replaced it but I put in the same thing I took out so as far as I know its original. I will have to play with it later tonight and see what I find. I have been thinking it might be the head unit but not to sure.