So, I was running a bit hard and suddenly had to slow down, so I shifting into neutral while braking. And I started hearing a rattle sound, like some screws shaking around in a tin can. It happens in gear or in neutral while deaccelerating. It doesn't make the sound while idling or accelerating. I stopped and looked under the car and didn't see any leaks or anything strange. Any ideas as to what it could be?

 

could be anything man, i would recomend checking under the car make sure you dont have a lose hanger or somethin

 

With the clutch engaged...ie the pedal is not depressed...you often get a rattle from the throw-out bearing. It's more noise than anything else and it does it at idle...you just can't hear it. Park next to a wall and idle the engine...you'll hear it. It is very common and not much of a problem until the bearing begins to squeal which is F-body for 'replace me, I'm shot'

 

I parked and let it idle for a few minutes and did not hear anything. Also, after I shut off the car. I tried shaking the tips and they were both held securely. I shall diagnose the noise some more later when I leave for work. But so far, it only occurs when decelerating and either in neutral or in gear. It first occurred when I shifted from 5th to N and hit the brakes. All of a sudden I started hearing that stranger rattle. And it sounds exactly as if there was something shaking around in a tin can, which at first caused me to think maybe something in the exhaust system (custom longtube headers and Magnaflow exhaust welded by previous owner), but it only occurs when decelerating. Very strange.

 

Alright, this thing is pretty random. I was driving to work and it would randomly do it. But it drove great as always. Then on the way back (about 5 hours later) it didn't make a noise, until I got home and went over a speed bump in my neighborhood. After it it kept making that noise. I'll probably take it in to get an oil and filter change on Friday and see what my mechanic says.