Noise in Rear of Miata

Diane Hall · **Posted:** Tue Apr 13, 2004 2:42 pm

OK, so my street miata has developed a new noise. It's rotational, exists between ~30mph and ~50mph (regardless of gear choice), and sounds like "whuwhuwhuwhuwhu". I've tried 2 sets of wheels/tires, so it's not that easy. When doing circles left and right, there was no change in the noise. It sounds to Jason and me like it's coming from the middle of the back, but it's hard to really tell.

After reading posts on both Miata.net and specmiata.com, the likely culprit was a diff fluid change was needed. It had been 20K (bad me) so we did that on Sunday. Diff fluid, while dirty, wasn't low. Noise still exists with no change.

Bearing(s) come to mind, however it's a little early (107K miles should be more like 160K-180K) for those and the rear end "feels" solid, i.e. no weird play/slop in the back when driving. A friend who's a mechanic suggested the U-joint. I don't know what that is, much less whether I have one.

I come to ask you guys since one out of every 4 of us seems to have a Miata. Has anyone come across this? What was your solution?

Thanks for any suggestions.

Diane

AndersGreen · **Posted:** Tue Apr 13, 2004 4:25 pm

U-joint: Universal joint. Allows rotational motion to change its axis. You have them for your socket sets, and in your driveshaft too.

Like your drive shaft:

Like your socket set:

With this being the actual part that generally has problems (and perhaps the housing it sits in):

(Note to mods: only about 20k of image data)

David Spratte · **Posted:** Tue Apr 13, 2004 5:35 pm

Trunk Monkey. Have you fed it recently?

Does the sounds change with rate of travel? You list that it occurs between 30-50 mph, does it change tone as you change speed?

AdamMenges · **Posted:** Tue Apr 13, 2004 6:07 pm

My '92 has that same noise... I just put a Spec Miata exhaust on it to cover it up :wink:

Diane Hall · **Posted:** Tue Apr 13, 2004 6:42 pm

Anders - Thanks for the education.

Might be that.

David - The noise gets faster as the car goes faster. I suspect it doesn't really go away at 50mph. My guess is that it becomes almost constant, and blends in with the exhaust noise or something.

Adam - If I was sure it wasn't going to grenade (bearings, u-joint, etc), I'd use the "make something else louder to cover it up" strategy. Unfortunately, I believe this is not a non-issue. This is a sound the car has never made in the 70K miles I've owned it. (And it makes a lot of noises.)

Thanks. Keep it coming.

Dale Schendel · **Posted:** Tue Apr 13, 2004 11:06 pm

My Corolla had a simular noise, very little play but the wheel bearings were making the noise also. (other than a possible universal joint. which at first I thought it was)

David Spratte · **Posted:** Wed Apr 14, 2004 9:39 am

I'd guess you had a bearing kiss the wind a little early.

Someone correct me if I'm wrong, but if the sound is speed dependent and not gearing dependent, that would indicate bearing more than a U-joint. Right?

AndersGreen · **Posted:** Wed Apr 14, 2004 9:50 am

David Spratte wrote:

Someone correct me if I'm wrong, but if the sound is speed dependent and not gearing dependent, that would indicate bearing more than a U-joint. Right?

I'll correct you.

No. Both are still equally likely: both your drive shaft (containing U joint) and wheels (containing bearing) have their speed linearly dependant on the speed of the car. Clutch in does not stop your drive shaft spinning, unless you have one of those crazy double clutches, where one is in your tranny and a reduntant one in your rear differential.

I had a bad U joint on my van... It made bad noises at a certain speed, but much worse when taking a right hand turn. Somehow it got loaded when turning that way which made it more noticable. Could still hear it going straight, but not at all turning left.

Anders

David Spratte · **Posted:** Wed Apr 14, 2004 11:36 am

Thanks Anders. :oops:

(I'm still not changing my vote for bearing though.

)

Brad Mackey · **Posted:** Wed Apr 14, 2004 8:26 pm

CV Joint!! (One of 4 in the Miata drivetrain).
Diane, the "whuwhuwhuwhuwhu" you describe sounds exactly like same "whuwhuwhuwhuwhu" sound the guys on NPR's "Car Talk" make to duplicate a CV Joint problem!

Maybe you can call those guys. They're right up there in Boston with you near Woosta!

Dale Schendel · **Posted:** Wed Apr 14, 2004 9:44 pm

but also if the U-joint is excesively bad you'll have a massive vibration in the whole car. (I just did a 4runner with that problem, a little different but same principle)

Bob Nyberg · **Posted:** Thu May 06, 2004 11:19 pm

If the noise suddenly stops and the car won't go anywhere, look under the car. If the driveshaft is laying on the ground, it was the u-joint. If it isn't, it was a bearing or rear CV joint. Don't ask me how...........
From the Coroner School of Diagnosis :wink:

Diane Hall · **Posted:** Fri May 07, 2004 9:27 am

It was the right rear bearing. The left is starting to go too. *sigh* It is almost 10 years old though, so I can't complain too much.

Thanks for all the opinions.

AndersGreen · **Posted:** Fri May 07, 2004 10:31 am

Diane Hall wrote:

It was the right rear bearing.

Hooray! Something cheap!

Anders

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Noise in Rear of Miata

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