2010 Chevy Equinox. When making sharp turns as when parking into a parking space it vibrates or shudders from the rear or at least it seems to be coming from the rear. I have had it into my mechanic a couple of times. I did have a leaky power sterring pump which he changed. I have had new brake pads and rotors put on. Had the lube changed in differential with additive put in. Nothing is heating up. No noise going straight down the road. Only when turning it shudders or vibritates even with no pressure on brake pedal. At a loss