Ok guys, I've been asking a lot of questions lately, but I'm hoping I can get my truck back to perfect running order. I was revving my engine some after doing a seafoam treatment, and I realized with engine revs while in park, my speedometer rises, almost to 10 mph on high revs, say 4000 rpms. Any ideas what could cause this? Is this actually a problem, or maybe a malfunctioning sensor?

 

i wouldnt worry about it as long as it reads write while driveing

 

I just read over on S10forum that it appears to be a quirk about the s-series trucks. Thanks