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Old 08-09-2009, 10:33 PM   #1
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Default Whirring/Roaring from chassis @ 4k RPM

So my car has developed a bit of a "roar" at about 4k rpm. The noise only happens around 4k rpm and will appear in gear and out of gear (if I remember correctly. I'm pretty sure the noise is coming from the chassis (wheel bearing, differential, etc???).

A couple weeks ago I had my first track day on R-compounds and the noise developed after the track day. My first inclination is the noise is from a bad wheel bearing, but the noise doesn't seem to happen when cornering...

Anyone have any ideas what the problem might be? I have an HPDE this weekend @ Mid-Ohio and want to get the problem fixed before that.

Thanks for any help in advance. I tried searching but didn't find much.
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Old 08-09-2009, 10:35 PM   #2
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Post a vid of the noise it could be a lot of things...
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Old 08-10-2009, 09:30 AM   #3
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Have you changed your motor mounts yet?

If not, it's a good idea to upgrade to the stiffer Mazdaspeed competition mounts anyhow, and may be what is giving you a problem. Seems a likely casualty of a track day if they were original.

Were you missing 2-3 shifts?
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Old 08-10-2009, 11:48 AM   #4
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Motor mounts were changed to the Mazdaspeed ones when I did the turbo install.

Diff mount hasn't been changed though...

I will try to post a video, thanks guys.
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Old 08-10-2009, 04:23 PM   #5
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First off do you have stiff diff bushings? Stiffer motor mounts and diff bushings will give you a lot more road noise.

If it is your wheel bearing te noise should change pitch/levels when you vear the car side to side on the highway. (Likely the problem if you started noticing it after a track day.

Check your trans and diff fluid levels (should be doing this before tracking the the car, like every event)

So check to see if its happening,

1. In gear/out of gear
2. Load/ no load (accel/cruise)
3. When applying load on the the wheel bearings (swerving side to side at speed)
4. Check fluid levels (trans and diff)

Hope this helps, surely you don't NEED a video of a noise to diagnose the problem, could help but there are only afew things that cause the type of noise your describing.


-Dean
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Old 08-10-2009, 05:20 PM   #6
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In response to Dean;

The engine mounts have been replaced w/ the Mazdaspeed parts, probably 5k miles ago (some track, some street). The diff mount is stock, 150k mile original I would assume.

The trans and diff fluid were changed before my second to last event. I planned on checking them.

The noise seems to be independent of in/out of gear and load. All that seems to effect it is speed, and the only speed it seems to appear is ~40mph. Cornering makes the noise go away, if I remember correctly.

Sorry my first post was so vague, I meant to add more of this info. I'll try to get a better feel for what's going on, it's kind of difficult to hear with the straight pipe exhaust on though...
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Old 08-10-2009, 05:22 PM   #7
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Sounds like a wheel bearing. The noise may go away when you turn to the side with the bad bearing (less load on the bearing), and get louder when turning to the opposite side (more load on bearing).
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