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Old 09-25-2007, 11:21 PM   #1
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Default Rear End Noise Questions

I posted this at .net too, but you guys seem to have more knowledge of swaps so maybe I overlooked something. I posted up about this a few months ago and haven't been able to figure it out. So before I dump any more time or money into the problem...



I have a 1990 w/ a Torsen unit from a 94. I swapped the knuckles, hubs, axles, and unit from the 94 that had about 110K or so miles on it.

At speeds over...say 30mph a whining sounds starts to occur from the rear...at 65-70 it is very LOUD...kinda like a full spool or posi unit sounds in a drag car. As in, louder than my aftermarket exhaust at cruise. It does it regardless of throttle application, clutch etc.

KICKER: When I turn right hard, or jerk it right, the noise stops, or gets much quieter, I can't tell, but it goes away for a second.


I've tried a few things (swapping out PPF, because my old one was slightly bent, changing driveshaft orientation, etc, etc.)

I can't figure out what it is, and these are the only three options I can think of.

-The rear wheel bearings, I've heard fronts going out, more of a thump, thump, but I've never heard what a rear sounds like on these cars. (they are separate from the hub in the rear correct?) - Because of the right turn making the sound stop, this could be a possibility?

-Could it be the CV/Universal Joints (whatever they are actually called) on the axles? How do I check?

-Could it be the backlash is setup wrong? The guy I bought it from said it was perfectly quite when he pulled it and I have no reason not to believe him. I didn't mess with anything on the inside.

Idea guys?

Last edited by miatamania; 09-25-2007 at 11:40 PM.
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Old 09-25-2007, 11:41 PM   #2
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i've had a bad rear hub/wheel bearing on a miata and it was much deeper sounding than what could be described as whining.
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Old 09-25-2007, 11:44 PM   #3
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That sounds dead on for a wheel bearing. Usually when they go bad and you turn hard to one side the noise goes away.

I'm not sure how the Miata ones are set up but you should be able to jack up the rear and shake the tire side to side, then up and down to check. Have a quick peek behind the tire while someone else shakes it to see exactly what, if anything, is moving.
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Old 09-26-2007, 01:54 AM   #4
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it might be your input shaft bearings or axel bearings. i had my input shaft bearing go out on mine its not that hard to do........ theres only one real way to check universal joints/cv's, jack up the car slide out the shaft(might need some persuasion, open the boot and look at the bearings and the shafts that the bearings sit on and see iff they are worn out.
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Old 09-26-2007, 02:33 AM   #5
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Sounds like wheel bearings if the noise goes away when you turn. That's my bet.
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Old 09-26-2007, 02:40 PM   #6
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Thats what I'm hoping...the nuts are pretty rusted and have over 100k on them...might as well try to replace them anyway. x.X
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Old 10-17-2008, 03:19 PM   #7
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so a bump from a year back... What did you do, have a new bearing pressed into the rear hub or did you replace the axle/CV joint? Did it make the sound go away?
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Old 10-17-2008, 04:39 PM   #8
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wheel bearing gets my vote. if you would have clutch-type diff, id say you didnt set your backlash properly...
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Old 10-17-2008, 04:41 PM   #9
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jesus christ. i just realized that this thread is ******* OLD! noob - dont resurrect old threads ever again please... next time create new thread and say that you looked at this thread and didnt find your answer. PLEASE!
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