According to my GPS unit, my speedo is reading 3 mph faster than what the gps says I'm going. Speedo says 60, gps says 57. I know the speed sensor is an electronic sensor but is there any way to calibrate or correct this problem? I know the GPS is pretty accurate becasue I've used it other cars and the speedo and GPS match. Any ideas?

Are your wheels and tires factory sized? properly filled with air? If they are factory correct and filled I would do additional tests on the speed sensor itself. Generally, they are usually functional or not functional, not often do they work but off by a percentage or two. Of course, at 30 MPH on the speedo, what does the GPS read? Does the speedo needle go down to 0, or just above?

There'* nothing you can change on the sensor. You see, the sensor reads pulses, the cars computer knows how many pulses is one turn of the tire, and it knows how far forward the car moves with each turn of the tire. With that it knows how fast you are going. Your tires are smaller the stock, and that'* throwing you off by about 5% or so. So you either have smaller tires, your your tires are worn down.

Most likely it'* a tired speedo in the cluster

Tires like new and factory correct sizing. Guess I won't F with it until it quits (which will probably be right after I figure out what the shuddering problem is).