I have the ultra-gauge setup on all my rigs and I like the unit. One of them has decided to act up. All readings are good except MPH. It reads about half of actual speed. I have tried unplugging/replugging it with no luck. Before I order a new one, has anybody come across this?

 

Since you have multiples maybe try it in another vehicle or pull one from another vehicle to verify. It sounds like something that the manufacturer might be able to fix with software.

 

Is there a factory reset option? Do that and let it reload everything.

 

I'd guess it is your VSS, not your Ultragauge.

To test, swap one of your other UG's into the truck and see what it says.