I am getting a metallic grinding noise from my front end when going up an incline. If you let off on the gas the noise goes away. If you give it more gas the grinding gets louder and then there is a loud bang as if the gear is engaging. It happens at all speeds 25mph to 80mph, as long as you are going up an incline. Took it to the dealer 3 times and they cant replicate it. It happens to me almost every drive but not always. any thoughts?