G.M. used these adapters on practically all there trucks with manual trans. They fine tune the speedo with these. I keep a bunch of them around & check the odometer with the freeway mile markers. I find one that is close to the amount of change needed. If it is the opposite of what I want I take the gears out & switch them. You can pick them up at the pull it yourself lots. The checkout guys don,t know what they are & don,t hardly charge much for them.
