My vacuum pump is running a lot and my auto 4x4 will not work all the time. When I have my air blowing out the vent or floor and I turn the 4x4 switch the air will switch to defrost when the selector is still on vent. My 4x4 hubs were recently replaced and that’s when it started. I tried disconnecting the air supply to the four wheel drive and plugged it off but the pump still runs a lot. ANy ideas? Thanks!!!