The Dana Spicer 770.04.010.01 or 7700401001 shim is a genuine Dana Spicer part sold by Pro Gear and Transmission.A shim is a thin precision spacer. In a heavy-duty axle it is how a gear’s mesh and a bearing’s preload get dialed in, so the right one has to go back in the right place. Match the number against your old shim or the parts book before ordering, and call us if you want help confirming proper fit.FeaturesGenuine Dana Spicer shimPart number 770.04.010.01Precision spacer used to dial in gear mesh and bearing preload in a heavy-duty axleCall us to confirm proper fit