Subaru Legacy:

Whine in drive train between 45-50 mph

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#1 11/10/2015 1:01 PM

GSVorder
New member
Registered: 11/10/2015
Posts: 1

Whine in drive train between 45-50 mph

2005 Legacy (non-turbo) with about 95,000 miles.  I am the original owner and there is nothing unusual or any crash damage or anything like that in its history and regular maintenance and necessary repairs have been done on a timely basis.

At around 45 to 50 mph I hear a low-frequency whine that sounds like a bearing to me. It is hard to determine location, but my best guess is center and toward the middle or rear.

This particular model had a recall for rear wheel bearing noise and both wheel bearings were replaced at around 75,000 to 80,000 miles.  One bearing was under the extended warranty and was replaced by Subaru, the other bearing went out right after the warranty expired and was replaced with a Detroit Axle replacement hub. The front and rear differential grease was changed at the same time and did not show any signs of abnormal wear, but it was time to be changed.  The differential grease was conventional and not synthetic, but it met requirements.

The noise is not related to engine RPM, does not change under acceleration, deceleration or coasting or the transmission gear selection (at least the top two gears at that speed). The noise is the same in a straight-line and through cornering.  I checked all the CV boots - inner/outer, front/back, no grease leaks from the differentials or transmission. The U-joints on the drive shaft seem pretty solid, really could not get a good feel or look at the center carrier bearing on the rear drive-shaft ( above the exhaust and heat shields).

What I did try was to disable the AWD and make the car only FWD by inserting a fuse to disable the AWD system.  This procedure is recommended when running the spare tire and is described in the owner's manual.  I am not using the spare tire, just disabling the AWD system. Well, my noise went away when I disabled the AWD and comes back when I enable the AWD system.

What I don't know is what the fuse is enabling/disabling and what I should suspect as a source of the noise.  I would  really appreciate some help and any ideas.

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#2 11/10/2015 4:56 PM

TechHelp2
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Registered: 11/24/2009
Posts: 1295

Re: Whine in drive train between 45-50 mph

From what I understand is when you install the FWD fuse it applies voltage to a solenoid that disables the rear wheels of the AWD system.

When you do this you take the engine load off the rear wheels. I would have the drive shaft center bearing checked before you check the rest of the transmission.

You would need to put the car on a lift and run the car in drive. With the car running find the speed of the car on the lift where the noise starts and start looking with a stethoscope to locate the defective bearing.


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