So what to look for in a used speedometer.... In most cases, The seller will photograph the instrument while it rests on its input. If that light bias force is lifting the needle at all, that is showing the wear there. And some wear is expected. I might buy and install one with 5mph lift if the price was right but any more than 7 mph, keep on shopping. In any case you'll need to clean the input and route that cable in as neutral as possible. Good luck
