I know this isn't Mazda related but we have a lot of car guys here and I'm just trying to figure out what is causing this noise in my Mustang. I made a recording and uploaded it to Youtube.

The sound does not happen at idle. It does not happen when the clutch pedal is pressed in whether sitting still or driving down the road. It is loudest under load accelerating or decelerating. It is not gear dependent, just gets faster the faster I'm going. Any ideas?

[ame="http://www.youtube.com/watch?v=tl5M-pcRHRg"]Mustang Drivetrain Noise - YouTube[/ame]

Flux capacitor?

That is the strangest noise I've ever heard

Sounds to me like something rubbing. Maybe something around your driveshaft came loose and is touching it slightly?? Dunno. Crazy sound.

Maybe put it up on the lift and check it?

It wouldn't be driveshaft related if it isn't speed related. and it doesn't sound line a u-joint. It isn't the tranny because it isn't gear related.

My first thought would be the serpentine belt or idler pulley. Sometimes they won't make noise if you just rev on the motor without a load.

My second thought would be the clutch or bearings (throwout or pilot).

Well, I can throw it on the dyno and we can run it and hear the noise, or we can throw it on the lift and see if its something rattling against something else...

Andyscums wrote:That is the strangest noise I've ever heard

Ditto. That would bug the crap out of me.

Some good info and offer. I could see that being belt/pulley related. Remember that time when everyone misdiagnosed? Ha ha

It isn't on the engine if it isn't affected by what gear you're in. This means that if it's something in the drivetrain it's trans output, driveshaft, rear diff, or wheel bearings. It almost sounds like something rubbing on a tire. The fact that it gets louder under accel/decel suggests to me that it's drivetrain related. Maybe a bad bearing in the trans output or pinion bearing? What have you done to diagnose or inspect it so far? How many miles are on it? Has the car spent time at the track or see hard launches on a regular basis? Bearing seems unlikely given the age of the car, but could have failed under abuse. I agree with D, could be something rubbing on the driveshaft.

RX-7 Chris wrote:It wouldn't be driveshaft related if it isn't speed related. and it doesn't sound line a u-joint. It isn't the tranny because it isn't gear related.

My first thought would be the serpentine belt or idler pulley. Sometimes they won't make noise if you just rev on the motor without a load.

My second thought would be the clutch or bearings (throwout or pilot).

It is speed related. It's not a belt for sure. Haven't done much troubleshooting because I don't have a lift and it doesn't happen at idle. I'm going to try rotating the driveshaft with the rear wheels in the air and see if something is rubbing.

Car has 13k miles and has seen about 3 days at the dragstrip and one day at a road course, along with 2 other very short trips to a road course (one 20 min session each), so not a ton of abuse.

aaa, I didn't realize it was speed related. I would start with checking the drive shaft. you should easily see if something is rubbing.

I would be really surprised if it was a wheel bearing with only 13k on it but you never know. I would probably lean on something rubbing.

If you want, I could look at it. I don't think I live that far from you.

erod550 wrote:Car has 13k miles and has seen about 3 days at the dragstrip and one day at a road course, along with 2 other very short trips to a road course (one 20 min session each), so not a ton of abuse.

You could have popped a bearing somewhere, but that seems doubtful. I'd guess something is rubbing somewhere. Check the wheelwells, too.

Wheel weight fall off?

Thought of another possibility, although it seems unlikely as well: stuck caliper.

No vibrations so it's not a wheel weight. Doesn't pull to one side like a stuck caliper would cause. I got under the car yesterday and spun the wheels and nothing is rubbing. Driveshaft spins freely. Even tried putting it in gear and got the wheels going about 20mph in the air and it wouldn't make the noise with no resistance on the wheels.

I double checked that my adjustable upper control arm's nut was tightened down. A while ago I was getting a vibration above 70mph and it turned out that nut was loose and my pinion angle was off. I fixed it right away though and it's still tight and the pinion angle is still good, about -2 degrees.

I decided to just take it in to the dealer and let them figure it out. I'm hoping they don't screw me and try to blame my mods for the failure, unless it's something that could have indeed been caused by the pinion angle being off for that short time and causing early wear on something. Then I'll just suck it up and pay to have it fixed, unless it's a problem with the driveshaft, in which case I will not be buying another stock 2-piece pos. I'll get a one-piece aluminum one.