my 2002 ford ranger 3.0L V6 is idling up to 1800 rpm with it being parked, running with AC on. needing help to figure this one out. Also when i go to put the vehicle in drive I feel from the back axle a hard thud when it goes into gear. From what I know the rear end of this vehicle has been checked but the 80/90 has never been replaced. Also the rear end axle is hot almost at the point I'm not able to touch it. from the military when it gets to that point it can cook off and destroy alot of things in the process. Any help is greatly appreciated. All comments I thank you ahead of time.