i have 94 Z-28 A/T and speedometer picks and chooses when it wants to work.

anybody with any ideas what's going on??????

 

You may have a faulty vehicle speed sensor (VSS) on the tailshaft of the tranny. If you do, it will set a code - have you scaneed it for codes?

If there is no code for the VSS, the signal is consistantly reaching the PCM, so the problem would be the wir from the PCM to the cluster, or the speedo itself. Does the odometer still work, when the speedo stops?

 

no codes are showing up.

yes, the odometer is still working even when speedometer is not.

 

I''d say you need a new cluster.