Over the past several weeks I've learned how many parts are driven by vaccuum pressure. Unbelieveable! I hit a deer (3rd one this year) and busted up my actuator shifter located on the back of my front axle. This too is run by vaccuum pressure. Engine started running like crap. Started slowly leaking front differential oil. Bolts all rusted, got lucky, replaced it and my truck has never run better. Heard some other small leaks in different vaccuum tubes and fixed them with drip tubing used for gardening.