Subaru Outback Forums banner

Need some help with diagnosis, please. Wheel bearing? Differential?

1K views 4 replies 4 participants last post by  idosubaru 
#1 ·
Hi everyone,

I apologize for the long and boring post in advance, but I'd greatly appreciate any help with diagnoising a particularly nagging noise issue. Thanks in advance if you read on! :smile2:

Since approx. mid-December(~68K miles), my very base model '09 5MT Outback (now w/ 71K) miles has been exhibiting a noise at speeds between about 25-70 mph.

The noise can best be described as a relatively low-pitched growl or hum, not a whine, squeal or grind. As noted, it begins at about 25 mph and seems to almost completely go away above 70 mph, although perhaps it just just drowned out by road noise.

The noise seems to be coming from somewhere in the front of the car. I initially though it was from the front passenger's side, but after being driven as a passenger in my own car yesterday, I think the noise may be more central, although I cannot be sure.

Once it begins, the sound does not seem to significantly increase in volume or change pitch through the speed range (maybe it's just a bit louder at higher speed), and it is independent of throttle position, brake position, engine load, gear selection, or neutral/in gear. It happens with both my all-season or winter tires on.

One interesting thing is that the sound changes significantly in pitch (i.e., sounds 'higher/faster') with a slight turn of the wheel, particularly when done while coasting in neutral at ~40-50 mph (there is a stretch of highway on my commute where I have tried this as I approach an off-ramp). I can't recall if it's the same if I turn the wheel right or left, buit I believe it happens in either direction. That said, the pitch also changes in the same manner when the wheel is turned slightly while in gear and under load at these speeds; it's just more noticeable in a neutral coast as there is less engine noise to drown it out.

Also of note, but likely unrelated, is that the sound only appears to have started after my car sat undriven for about a week and a half, while I was away on vacation in early December. When I resumed driving, I noticed that my steering wheel feel felt somehow different, especially at very low (bumper-to-bumper traffic) speeds - almost like there was a stutter in the P/S system (air in the lines from sitting? is that even possible?). This at first led me to think there might be an issue with the pump that is responsible for the whining/growling noise (particularly due to the change in pitch with steering input, as described above) but I've all but ruled this out due to it's lack of correlation with engine RPM, and the fact that the P/S pump sounds 'normal' at idle when checking under the hood.

Finally, I should note that I had the transmission and gear oil changed at a reputable Subaru dealer at approximately 63.5K miles, jut before a 3,000-mile summer road trip. The gear oil levels, odour and colour remain good, and the techs at the time didn't report any metal or other issues (although I don't know that they would have checked). I have also been experiencing relatively notchy shifting into some gears, which seems to come and go with no regular pattern, since about 55K miles. I chalk that up to my fair share of careless (grindy) shifts and hope it's not related to the current issue.

I'm inclined to think (and hope) that this is a wheel bearing issue and not a front diff problem. Any insight into the noise or further diagnosis (I do have access to a lift, but that relies on significantly inconveniencing a friend) would be appreciated. I apologize for the volume of text, but figured it's best to be thorough and detailed.

Thanks!
 
See less See more
#2 ·
Other than taking apart your hub assembly for visual verification that a wheel bearing is indeed going bad, the best idea I've seen suggested is to obtain a "heat gun" and take the temperature of your front wheels after driving long enough to get up to operating temp.

Point the device at all of your wheels and look for any temperature discrepancies amongst them.

Of course they (esp the fronts) will be warm from your drive, but if you notice that one is approx 50°F warmer than the others it is a good indication that the bearing for that wheel is failing.

These devices are available on ebay and amazon, other places as well I'm sure, and IMO worth trying.
 
#4 ·
if you are going to invest in a pistol grip thermometer, this one has enough range to read engine and exhaust temps too.

 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top