There is a strange nose coming from my rear. When I am going down a hill and apply the brakes SOMETIMES I hear this sound coming from the back of the car. Sounds like metal hitting together. I only hear it once in a while. I had the rear inspected by my mechanic and he couldnt find anything wrong??

 

First make sure it's coming from the rear portion of the car. Due to the way human hearing works sometimes this can play tricks. Turn your head 90 degrees when you hear the noise to look at the passenger door real quick, this will really help you isolate the location of the sound.

What kind of sound is it? Metal on metal grinding? How long does it last? Is it more like a thunk/bang? If so check for a broken transmission mount. This is very common and you can check by putting a jack under the transmission and SLOWLY AND GENTLY jacking up on it. If the transmission rises independently of the car the mount is broken. If you see the transmission and car start to rise up as one piece, the mount is good.

Get the back of the car up so you can take a look. Start by examining the driveshaft, see if anything could possible be touching like e-brake cables or exhaust. Keep in mind that driveline flex during certain engine load conditions (like downshifting for deceleration) could cause the exhaust to move one way or another more than you might think. Check carefully all along the driveshaft and along the axle for possible points of contact. If you don't find anything check out the brakes.

How long since you serviced the rear brakes? Based on your screen name I'll assume you have rear disk brakes. Take off the wheels and take a quick look. Are the pads good? How old are they? Maybe have somebody give the e-brake a quick yank just to see if you hear anything funny. Are the rotors in good shape?

 

Its the rear end cuz it started making the nose right after I put it in about 3 months ago. It sounds like metal on metal. Like a clang, only lasts like a second. Very strange. Everything else is fine.