My speedo is officially wrong

I have a question first...

when you're stopped....does it sit at 0mph?

 

Do you have aftermarket rims, or a different to stock gearbox?

 

Do you have access to a different gauge cluster to throw in and try?

 

Correct me if I'm wrong, but I believe different wheel size will not affect the speedometer reading at a certain RPM. No matter what circumference tires you put on, if you put the car in 5th gear and bring the revs up to ~3000rpm the speedo should read 60mph.

If the tires are larger than stock you will *actually* be doing more than 60mph, but the speedo will still read 60. Likewise, if the tires are smaller than stock, you will *actually* (as in police radar) be doing less than 60, but the speedo will still read 60.

Does the needle on the speedo bounce around at all? Is it *consistently* wrong, or does it vary it all? If it's bouncing or reading erratically, its probably a bad speedo cable. If not, its either the wrong tranny/speedo gear, or a bad cluster.

 

What you could do is to a Auto wrecking place it and get a cluster there, Cuz most auto wrecking place have a 30 day return deal. SO you can go buy one and see if it is the cluster and if it isn't then you can take it and get your money back.

 

Your first and second paragraph contradict each other.

 

My statements are not contradictory.

While different size tires *will* affect your speed going down the highway, they will not affect the ratio of revs to mph(reading) for a particular gear. As per greg's first post, in 5th gear his speedo reads 59mph at 2500 rpm. We agreed this is too low for a GT-S. I am saying this discrepancy cannot be caused by different size tires. In 5th gear, now matter what size tires are on the car, 60mph should be ~3000 revs. Whether you are actually *traveling* at 60mph is a different story. I am only talking about the speedo "reading".

 

Unfortunately the manual is not very helpful unless you have a speedometer tester.