I bought this 2003 Z71 ext cab 5.3 L used last year it has 91K on it. so today I changed the plugs wires, PCV valve, fuel filter rear differential fluid, gasket and flushed the radiator. Tomorrow I will do the front differential and the transfer case. The trans is next week my buddy is helping with that. I put all OEM back in the truck except the rear I got Amsoil sever gear 75w90