QU40543 King Pin Key for Dana 44HD, Dana 60, Dana 70 Upper King Pin Bushings fits in slots machined in your upper king pin and QU40327 Upper King Pin Bushing to lock them together. QU40543 is used on Chevy, Dodge, GMC, and International Dana 44HD, Jeep M715 Dana 60, and Dodge, International Dana 70 Closed Knuckle Front Axles.
This is one of those simple, but often overlooked parts that should be replaced at every axle service. If the Key fails, your King Pin will simply rotate inside the Bushing causing rapid wear and poor steering.
As far as I can remember, all the Upper King Pins have only one Key Slot, but since the Bushing has two slots, there may be some axles that use King Pins with two slots 180 apart. Order 2 or 4 Keys as needed.