I took my 07' KC 4x4 to the dealer today for an audible tick coming from the drivers side. I had already listended to everything and knew it was valvetrain related. The dealer sent me away and stated that they needed to order "shims" to correct the problem. When asked for clarification, I was sent away and told it would be fixed. Does anyone know what these "shims" are and what their purpose is? I don't want to end up with more problems down the road...please advise!