I have been stumped on issues with my 4x4 system. When engaged there is a loud pop from the driver side front while driving. Only some times i get the "check 4x4" wrench light. I seem to get the pop more when it is turning. I replaced the iwe actuator as well as the cv shaft. I KNOW the tie rod is bad because it has a fair amount of play in it. But would that be causing the issue? Vaccumm is working fine in the system.