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Unread 02-10-2013, 10:30 AM   #1
Kenmo
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1985 CJ7 
 
Join Date: Sep 2012
Location: Gilmore, ohio
Posts: 6
Rear drivetrain noise above 30mph

I need some help tracking down what I think is a bearing noise from either my Dana 300 or the AMC 20.
In two WD 30mph and above, under load, meaning when I'm on the gas I am getting what almost sounds like tire whine (Bearing noise?). It goes away in 4 lock or when coasting. It gets louder the faster I go. I removed the rear driveshaft and took a drive in 4 lock and it is quiet.
I had the Txfer case out when I rebuilt the T177 a few weeks ago and could not feel anything funky in the bearings. I have new universals on the rear driveshaft. I lifted the rear and cannot feel or hear anything in the rear axle.

Anybody have any tips on isolating noises between the output of the Dana 300 from the rear axle?
Thanks

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Unread 02-10-2013, 12:36 PM   #2
S76
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1984 CJ7 
 
Join Date: Nov 2012
Location: Stafford Springs, CT
Posts: 389
If it were mine, I would jack up the rear and run it in gear using the brake to simulate the load to reproduce the noise. Using a long screwdriver to my ear I would listen to the Dana output bearing and to the 20 pinion bearings. The screwdriver acts like a stethoscope and you will hear where the noise is coming from. Or you can by an automotive stethoscope to do the same thing.

However, Having someone run it in gear while you crawl underneath is dangerous. Or, you could take it to a garage and have them do it on a lift.

My guess is ring or pinion bearings.
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Unread 02-10-2013, 12:42 PM   #3
Noplainsdrifter
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1974 CJ5 
 
Join Date: Jul 2011
Location: Hillsboro, Or
Posts: 513
Did you replace both u-joints? That's usually the culprit.
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Unread 02-11-2013, 09:19 PM   #4
S76
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1984 CJ7 
 
Join Date: Nov 2012
Location: Stafford Springs, CT
Posts: 389
Quote:
Originally Posted by Noplainsdrifter View Post
Did you replace both u-joints? That's usually the culprit.
" I have new universals on the rear driveshaft. I lifted the rear and cannot feel or hear anything in the rear axle."
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Unread 02-11-2013, 09:25 PM   #5
Double8racer
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1984 CJ7 
 
Join Date: Oct 2012
Location: Cleveland, Ohio
Posts: 32
check if there is any play on the rear wheels
mine just threw a outer wheel bearing and it took me melting a set of pads and a few hrs work to find it
Jack it up and see if there is any play in bearing up down left and right
noise was similar to yours but changes tone more in left or right hand turns/curves
good luck
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