2002 XC rear whine

[mhrir]

I have a 2002 XC w/ 37,000 miles. Recently it has started making a whirring or whining noise from the rear. It starts becoming noticeable around 40mph. Applying power decreases the noise and coasting increases it.

It is not a wheel bearing noise in my opinion since I replaced the front wheel bearing about 6 months ago and am familiar with that sound.

Some searching on the forum suggests is could be the viscous coupler or pinion bearing.

With such low miles are there any suggestions where to start diagnosing?

[Aviator]

Check your wheel bearings.....start off simple.

Dave.

[mhrir]

Wheel bearing noise is dependent with wheel speed. It doesn't go away when power is applied. This issue is directly affected by application of throttle and coasting. Likely that is not the problem.

I topped up the differential oil but it only took 2-3 oz before coming out the fill hole. There is some residue on the viscous coupler on the end towards the diff which makes me think the pinion seal is leaking slightly.

So it seems I am down to the viscous coupler or pinion bearing. From what I have read it is less likely to be the coupler. Anyone else have any insight to offer?

[Astro14]

Depends on the wheel bearing. Power on/off changes the load on a driven wheel and can change the pitch of the noise, reducing or increasing the intensity.

Just had a rear axle bearing go out on the 4 Runner - noise changed with power on/off and at mid-throttle, I was able to quiet it down for the limp home...

[Willy]

I had something quite similar, but on the front side of the car. Sounded exactly like a wheel bearing.
It turned out to be a tire problem, the outer track had become cupped and made the whirring noise.
I know it doesn't sound likely, but it is worth taking a look at, perhaps swapping tires.
Willy