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Wowowow noise when turning

I’ve got a 2002 subaru legacy wagon, 150k miles. Over the past year or so (a real guess, can’t really remember when it started) it’s developed a wowowow noise that happens when turning. The car has to be moving - just turning the steering wheel while stationary does not make any noise. I can’t tell if it’s only coming from left or right side of the car or the front or back. It also doesn’t happen when driving in a straight line. The wow’s are faster when the car is going faster but the frequency is very roughly 4 per second at 40 mph. The noise itself is pretty low and grumbly, and kind of sounds like James Earl Jones saying “wow wow wow wow”.

Any help is appreciated!

My guess at this stage would be a problem with the rack or the power steering pump. The belt driving the pump may also be the problem.

A good mechanic can zero in on the real cause very quickly. Steering problems are not that hard to diagnose.

If the noise only occurs when the vehicle is moving and turning, then I would ask when was the last time the differential fluids were changed?

The differentials are what allow the wheels to rotate at different rates while turning. When the fluid in the differentials breaks down, the gears in the differentials can start to howl.

This doesn’t occur when driving straight because the wheels are rotating at the same rate.


I think that Tester is on the right track, but I think it is also important to consider the center viscous coupler as a possible source of the noise.

Has the car ever been run with mis-matched tires, or with tires that weren’t rotated on a consistent mileage basis, or with a donut spare in place for an extended period of time?
I ask that question because any of those situations can result in excessive wear of the center viscous coupler.

Thanks Doc, Tester, and VDC for your help.

The last time the differential fluid was changed was probably 2 1/2 years ago (~20k miles ago). Since then it’s gotten regular oil changes but that’s about it.

I think that was the last time the tires were rotated too. I don’t think it’s ever had mismatched tires or a donut.

If the last time that the tires were rotated was about 20k miles ago, then you may have done damage to the center viscous coupler.

Subaru specifies tire rotation every 7,500 miles, but whether someone chooses to rotate the tires on an AWD vehicle more frequently–ergo, every 5k miles as Toyota specifies–or if they might want to stretch things to 10k miles, going 20k miles without tire rotation on an AWD vehicle is just…asking for trouble, IMHO…and unfortunately, there is frequently a price that one has to pay for ignoring maintenance specifications.

As to the OP’s statement, “the differential fluid was changed was probably 2 1/2 years ago. Since then it’s gotten regular oil changes but that’s about it”, if you have not done things like…changing the brake fluid, rotating the tires, and…possibly…other specified maintenance procedures, you may have wound up shooting yourself in the foot in the process of…theoretically… trying to save money on maintenance.

Fair enough. I will fully admit my negligence. Is there any easy way to check if that’s the issue?

Also, I just checked my records and I don’t think the differential fluid was changed 2 1/2 years ago. I got the car at about 95k miles in 2009 and have never changed it, but I don’t know if it was changed before that.

Please list the exact maintenance that your car has received since you took possession of it.
At this point, I think that you have likely skipped a lot of the required maintenance, but I am willing to be proven wrong by what you might post.

Alright. Don’t think you will be proven wrong. Just remember I’m trying to reform!

Other than oil changes every 6 months or so (about 4k miles):
2009/95k - I had to replace the timing belt (it needed it when I got the car)
2010/103k - front/rear diff fluid change (totally forgot about this! just found the receipt in a folder)
2010/105k - new battery and headlight bulbs
2011/110k - engine coolant change
2013/120k - new starter solenoid contacts
2013/123k - 120k service (shop gave me long list of things they checked, they also replaced air filter, brake fluid, coolant, and spark plugs)
2014/135k - repaired flange between muffler and midpipe w/ split flanges

I rest my case.
This appears to be yet another case of somebody who ignored the vehicle’s manufacturer’s maintenance schedule, and–possibly–in an attempt to “save money”, wound up shooting himself in the foot.

Whether this relates to just your present vehicle or all of the ones that you will own in the future, please try to remember that the cost of specified maintenance is invariably cheaper than the repairs that will inevitably result from ignoring that maintenance schedule.

Trust me…those simple tire rotations would have been a relative bargain, as compared to the repair costs that you are likely facing at this point.

Diff fluids were change six years/47,000 miles ago.

That’s what I would do first is change the fluids.

Cheap and may get rid of the noise.


Change the diff fluids as @Tester said. Tires are the biggest killer of awd cars. Replace all 4 and rotate them every 7500 miles.

Symptom can also be associated with a failing wheel bearing or problem with a tire. If it makes the noise only when turning to the right say, that could indicate a problem with the left wheel bearing or left tires. You can’t inspect the wheel bearing yourself probably, but you can take a look at the tires on that side. Notice anything unusual, like patterns in the tread wear?


The OP states, “over the past year or so”.

Wouldn’t you think that if there were a problem with a wheel bearing or a tire over this duration of time it would have revealed itself by now?

You’re guessing again.


Hard to say without seeing the car or hearing the sound it is making. Let’s see what the result is once it is properly diagnosed.

Thanks again to everyone for your help and responses.

The sound happens with both left and right turns.

I’ll take a look at the tires tomorrow when it’s light out and see if there’s any strange wear patterns that are visible to my untrained eyes.

I don’t have a real tread depth gauge (just found out via google that those even exist) but I do have normal 6 inch calipers. I used those to try and measure the tread depth and came up with:

Left front: 0.11" (3.5/32)
Right front: 0.08" (2.6/32)
Left rear: 0.13" (4.2/32)
Right rear: 0.13" (4.2/32)

I checked the dipstick for the front differential and it was on the low side of the range and had a honey-ish color and texture. I can’t get to the rear easily.

I have to take the car to a shop anyway for emissions testing because I just moved to a state that requires it but I’ll tell them about the noise and tire history and see what they say.

A comment: you should replace those 4 tires. 4/32 is considered the point where the tires start to lose traction in rain or snow.

2/32 is the legal requirement but 4/32 is the recommendation.

I agree with Bill Russell that those tires need to be replaced, and I hope that the OP will remember to have them rotated on a consistent basis from now on. That won’t un-do the probable damage to the center viscous coupler, but at least it would keep him from damaging the new one that will soon be needed as a result of those mis-matched tires.

Subaru specifies rotation every 7,500 miles, but any consistent interval is okay, as long as it isn’t too many miles. 10k would be too long an interval, and anything less than 5k would be too short an interval. Try to stick with a mileage interval that you will remember, and that jives with your oil change regimen.

I forgot this is a Subaru, so I change my recommendation that you get new tires to a strong recommendation. I think Subaru’s spec is 2/32 difference in tread depth. And, yes, have them rotated on a regular basis, probably when you do an oil change.

Be sure to let us know the diagnosis and result OP. Best of luck.