So my "new" camaro has a speedo and tacho that are obviously reading wrong. Sitting on 60mph the gauge reads about 80mph and the tacho idles at about 2500rpm when it's obvioulsy not revving that hard. It you give it full trottle it will reach redline when it feels like its actually doing around 4000rpm. I believe this is also confusing the transmission and causing it too shift early, at a slow cuise speed it will shift into top gear far too early and cause the car the struggle and shake at low revs.

I have no idea how the instruments get their info from the engine but is this a common problem? What could be wrong?

Before anyone thinks about diff gears, the gears are standard.

 

The first things that come to mind - The 90-92 Camaro tachs are notorious for having problems - There is a sticky in the Electronics section that will help fix it - It worked on mine.

As for the speedo, the most likely scenario is probably (a) Your VSS is bad, or (b) someone has changed either gears or the tires are not the correct size, or (c) the transmission was replaced and the driven gear in the new transmission was not the same as the original.

The tach is any easy thing to fix, as for the speedo, those are where I'd start, but a bit harder to identify.

 

Well, i learned pretty quickly that the gauge clusters on 3rd gens are pretty much crap. I don't know if the ECU would affect that or not, but if someone tells you that, i think i have an extra one sitting around somewhere. Perhaps i could send it to you if you have an early car. Another thing to think about is your Transmission. If the transmission was swapped, it might have a different speedo gear set. Are your tires stock height? Do you have access to another Cluster? I know that here in Shreveport we have 4 U-Pull-It yards and Clusters are cheap. If you can get another cluster for cheap, you could rule that out by testing another.

 

Thanks for the help guys, tranny and wheels are standard so it's definately a fault. Does the speedo calculate independantly of the tacho or does it use the rmp from the tacho to measure speed? The tacho is obviously unaffected by gearing because it is out of whack while the car is stationary. If the speedo then calculates speed from the bad rpm reading then that would explain that one too. I'll check out the sticky in the electronics section.

 

Tach and speedo are independent of each other.

Chances are either the VSS is bad or someone swapped transmissions at some point and the speedo gears inside were different than OEM.

 

my speedo isnt working either and the guy i bought it from did say he swapped the trany out for a Corvette trany but he didnt say what year it was ive only had the car about 2 weeks