speedo problem...HELP

[crate]

Since i got my truck off and on i have had a problem where the speedo and the tach stop working correctly, The tach will not move up or down just stays around 2, and the speedo doesn't move right, skips up/down in 5 mph movements. When this happens if i hit the dash, the guages will work fine again. I've been at a stop ligh and looked down and it said i was going 30 mph and tach at 2.

 

This happens off and on, might go a few weeks with nothing, then all of a sudden it comes back. When it starts to act up I dont feel any difference in how the truck runs/shifts. could this be just a bad cluster? or could this be a VSS sensor problem?

 

I've never got any type of error message when this happens. and nothing shows up on a scan.

 

This is on my 99 GMC Sierra NBS. Got it around 50k now have 114K and has done it off and on, and now would like to pin point this down.

 

Thanks

[GM-Tech]

Sounds like a cluster problem to me. We see this a bit in the newer ones, though I can't say I've seen it happen in a '99.

 

If the speedo ever stays above zero when the key's off, it's definitely the cluster.

[crate]

Thanks,

 

I have never noticed the speedo ever being above zero when key is off. But never really looked at that time, Next time it acts up, i'll check that.

 

At least for now it doesn't sound like it's the vss sensor, since if that was going bad it would have completely died now 60k miles into this problem. Guess i get a cheap one on ebay and see if it stops, if it does then i'll go ahead and get a better one with the trans temp.

 

thanks again.

[GM-Tech]

If it was the VSS, you'd have more problems than just the speedo.

[crate]

Okay, thanks.

 

The only problems is with the speedo and tach. All other guages work perfect, and no running/shifting problems with the truck

 

What are some of the issues if the VSS senor was going bad?