Can Anyone Please Help Diagnosing Rear End Noise ?

Would greatly appreciate anyone's help and/or opinion on diagnosing a quirky rear end noise.

Car is a stock (no mods at all) 06 Speed 6 GT (but was first put in service in 3/07 -- bought as a leftover)... Currently has 19,200 miles. About 7-8 months ago developed an intermittent rear end noise. But the performance of the car has not been affected in any significant way (yet). The noise seems to come from the rear end -- it does not seem to be correlated with any particular factor -- seems random as to when it happens -- happens in any gear, at any speed, also happens in neutral when decelerating/coasting,
happens when the car is cold or hot, happens in any kind of weather, comes and goes -- sometimes is noisy for 5 mins then disappears for an hour or tow hours, then may happen again for up to an hour continously...etc....No real pattern to it. The sound is rhythmic/periodic in nature -- varies with the speed of the car ...sounds like a rubbing type of noise -- the syllables
"rrrrrhhhh" "rrrrrrhhhhh" "rrrrrhhhh" come to mind. Not very loud but very audible if paying attention and VERY annoying.
Car has been brought to the dealer 3x for this problem -- twice they put it up un a lift and found no visible damage or rear end problems -- another time a mechanic took it for a ride with me and, of course, it didn't do it when he was in the car (though people riding in my car as passenger have heard it) -- so the dealer won't do anything for me.
However, 10 days ago -- I had a 4 wheel alignment done at the dealer and ever since then, the noise is no longer intermittent but constant.
I am tearing my hair out because (a) so many things might be causing it (bad bearing -- differential, cv, wheel bearing etc....etc... (b) the one time i will take it to a mechanic and do a test drive I just know it won't occur (c) the noise is SO annoying that I just can't live with it this way and (d) seems like dealer won't do anything until it ultimately causes a "catastrophic failure" (of course that will happen when the car is no longer under warranty ! )

I have included 2 sound files made with a handheld digital recorder from inside the car -- 1 is without the sound happening to provide a "baseline" of noise while the car is at highway speed and the other has the noise clearly audible as a rhythmic "rrrrrhing" which is constant throughout most of the 2nd sound file.

Any help or ideas greatly appreciated

Many thanks,
NWView attachment rearnoise.mp3

View attachment nonoise.mp3

Is it pretty loud? Im at work so I cant hear the soundbites. I have wierd vibrating noise coming from my rear end. I pulled the ebrake up one click to disengage the AWD and it goes away. Mine is like a pulsing noise once I get around 50 or 60 mph.

I haven't yet tried the ebrake thing.
Mine is a very regular rhythmic sound (when you get a chance, you can hear it clearly in the mp3 called "rearnoise") -- pretty loud -- happens at all different speeds in any gear or in neutral also ...
Don't really feel a vibration -- nor does the steering wheel vibrate at all, and the car drives fine -- no wheel vibration either -- just the loud, rhythimc "rrrrrhing" noise......

Ace,

This link might prove to be of a little help.
http://www.4x4now.com/gt0699.htm

The easiest thing to check is probably the wheel bearings. If you can jack up the car (with the wheels off the ground) try to move the rear wheels back and forth from side to side. If they move more than a 1/4" of an inch either way, you should pull the wheel off and check the bearing.

Being that your car is an '06, you should have a 50,000 mile warranty for 5 years. Granted, "noises" are not covered by the warranty, but if you have a quality service tech there ask him to go for a ride with you so he can hear the sound. The great techs know exactly what the sounds are.

Thanks -- I guess it is possible it is a bad wheel bearing but don't know why dealer wouldn't have seen this since they have supposedly looked when the car was up on the lift at least 3x at their shop....Plus the car doesn't seem to exhibit any driving behavior characteristic of a bad wheel bearing

Noise

I would do the bearing check on all 4 corners, and if you can get it high enough to get under you can do a few things with a stethoscope too. Just make sure you don't touch those moving parts.

It could also be tires. As most tire shops will tell you that high performance tires usually get a lot of road noise.

It's usually one of those sacrifice comfort for performance deals.

check yr axels

sounds like uneven tires to me.

rear end noise

1quickturbosix said:

Is it pretty loud? Im at work so I cant hear the soundbites. I have wierd vibrating noise coming from my rear end. I pulled the ebrake up one click to disengage the AWD and it goes away. Mine is like a pulsing noise once I get around 50 or 60 mph.

Click to expand...

If you disengage the AWD and the vibration and noise goes away, it is probably the inner CV joints. We have a car in our Honda (sorry) shop with the same symptoms. The local Mazda dealer said it was the diff., but after disassembly, we found the inner CV's completely shot on a relatively low mileage car.

I'd agree check the axles

Now that I think about it I was getting a little vibration before I blew up my first axle. I blew my second axle a few weeks ago, and it's something that has been more a pain this time around.

I've also been doing some research on this. Because of the way the rear diff is mounted and the LSD. You don't always notice it but you get some wheel hop when turning, and under hard acceleration. Mazdas aren't known for having the best CV joint, but are better than most stock CVs. If is starting to go you'll notice some abnormal play in the joint instead of in and out you'll see the half shaft kinda wobble if that makes sense. If you catch it early you will avoind other problems like break the diff mount/s.

If you do have a bad axle all it really takes is for it to blow like this is for to slip and then catch traction then BOOM. If you notice in the first pic look where the halfshaft went. Look for the boot at the top right of the pic. Don't take it to Mazda for them to diagnose this they have missed this TWICE before I'd had a problem.

06 Speed 6 MSP CAI, HKS SSQ BOV, Standback tuner, Magnaflow mufflers.