lately when i reverse the rear sound like a air horn for a few second it dosent happen all the time but every other reverse it does it, could this be the caliper sticking or the break pads worn down? before i go spend money on the wrong parts i was wondering if anyone experience this sound and fix it

 

Most likely your calipers are stuck.

 

Same thing happened to me on my trip to orlando. Calibers are stuck. Go get yourself a new caliber with new pads.

 

For the calipers where would be the best place to buy them (stealership, autostore)?

 

Ha, same exact thing happens to me. Search the forums. I remember seeing a how-to about how to get rid of this. Anyways, its really annoying and I will be replacing my brakes soon.