I have been having a problem with my speedometer on my truck. It will not register any speed until you have reached a speed close to 50 mph and then it works fine. I have confirmed that the speed being displayed is accurate with a hand held GPS unit all the way to 85 mph. Any thing less than 50 and nothing, it just drops to zero. I have a speedometer correction unit installed for the larger tires and have gone back and soldered all the spliced connections to no avail. Any help would be appreciated. 
