OK so here is the whole story. I have a 2004 Silverado that came with 16 inch wheels. I found a deal and put on some 2007 Tahoe wheels. Ov course with the tires being a little bigger I knew the spedometer was going to be off a little. It was about 4 miles an hour off at 75 mph. But after driving it for a bit the spedometer would drop down and read 20 mph and I was going 55 mph. So I figured maybe the computer was getting confused, so I pulled the battery terminal for a bit and reset it. It seemed to be working fine except it was off a little. Good excuse to get a Diablosport predator. So my predator came in and I am having a little problem with it programing the new tire size but Dialosport is working with me on that. This weekend I went on a long trip and after about an hour and a half of driving I noticed the spedometer was off about 10 mph and it got progressively worse. By the time we got to out hotel it would only read 0 mph. So I figured I would have to reset it again since I had just programed the truck with the predator the day before. When we got ready to leave today ( the truck sat overnight) it seemed to be back to about 4 mph off. Again on the way home the whole problem happened again. Even reseting it did not fix the problem. But after the truck sat for about 10 minutes the spedometer started working again. I am just out of warrranty but I do have an extended warranty ( non-GM). And this would be covered in that warranty. I just need them to be able to find a problem and not to have a no trouble found which I think I would be charged for the diagnostic. I just need some help into what might be cauisng this. Is it just the computer getting confused because of the difference it is seeing in rpm measurement and speed and such, or is there something really wrong with the gauge. Also one more thing. It seems that even when the spedometer is not working it can still calculate instant MPG that seems to be reasonable for the speed my GPS says I am going.
Thanks,
Bill