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Is this a nutty idea? I got an intermittant rumble up front, I think right side, on my 2008 Forester. It vibrated one day on the expressway until i pulled off and made a few left and right turns, but I really have no idea what caused it. Since then I hear a bump like a loose shock mount over bumps on certain roads at certain speeds. Tires are Avid Ascents at 12k miles and 32 pressure.

 

Anyhow I thought swapping the front axles side to side might be an interesting experiment, but since the noise or vibration only occurs sometimes, I don't know what the observed condition would be.

 

Will I be able to tell if the axle joint is damaged if I remove the axle? No clicking or other symptoms. I'm not a "throw hardware at it" type of person.

Edited by uniberp

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Your clunk may be the ball joint. Yes, the axles are interchangeable side to side, but i doubt that wil accomplish anything. A worn ball joint can case the wheel to shimmy if bad enough and will rattle on bumps.

 

If the ball joint fails, the wheel rips away pulling the axle out and cramming the tire into the fender sideways, leaving the car inoperable and damaged, if not crashed.

Edited by MilesFox

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Yup - what Miles said...

 

jack up the car, support it safely, and grab a tire at the 12 & 6 o'clock positions and try to wiggle it - see if there is any movement.

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Sorry if my comment seems so startling. But you would notice a bad ball joint if you attempted to swap axles.

 

I hear the rumbling occasionally still, and still it gets corrected with a few low speed tight turns. Kind of a pain when on the expressway.

 

I pulled off this morning and smelled hot boot rubber. Not split or anything, but I noticed the driver's side shaft can wiggle a little along the axis. The passenger side does not. I guess I got a tight or seizing bearing in there, probably heated up. As long as the boot is intact it probably won't catch fire.

 

Factory original axle with 80k miles.

 

 

 

At some point it will need attention

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wondering if your wheel bearing is ready to crap out.

That was going to be my thought.. my truck makes horrible grinding noises, every now and then, when bearings are going bad.

 

But if I am not mistaken you can test bearings by jacking up car and wiggling tire...  ?

Edited by LetteLizard

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That was going to be my thought.. my truck makes horrible grinding noises, every now and then, when bearings are going bad.

 

But if I am not mistaken you can test bearings by jacking up car and wiggling tire...  ?

 

 

Wheel bearings are ok. No runout at all. It happened again coming home on the expressway, a vibration, and when I applied the brakes a rhythmic grinding timed to wheel rotation. This time it seemed to come from the left front, previously I thought it was right.

 

Nothing loose with the axles, at all. I've done many axles on subarus and kinda know this stuff.

 

As I was checking the right front wheel I noticed a little blue plastic cone cap sitting on the control arm edge. It was a cap to a gear oil squeeze bottle. I don't think I ever changed that, but I may have

 

I checked the front diff and it seemed a little overfilled. 30k change recommended, so I did. The oil that came out was cleanish, I'm letting it settle overnight to see if sparkles settle.

 

It scares me when the noise happens, I can feel the grind in the brake pedal,  but it self-corrects every time.

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brake caliper sticking?

 

also, try swapping tires back to front.

 

New brakes since the first occurrence. Tires all new (<10k, rotated at 6k), aligned, since first occurence.

I'm hoping it was the slight overfill of the front diff causing a backlash of some kind.

Edited by uniberp

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Yup - what Miles said...

 

jack up the car, support it safely, and grab a tire at the 12 & 6 o'clock positions and try to wiggle it - see if there is any movement.

 

Wheel bearings are ok. No runout at all. It happened again coming home on the expressway, a vibration, and when I applied the brakes a rhythmic grinding timed to wheel rotation. This time it seemed to come from the left front, previously I thought it was right.

 

Nothing loose with the axles, at all. I've done many axles on subarus and kinda know this stuff.

 

As I was checking the right front wheel I noticed a little blue plastic cone cap sitting on the control arm edge. It was a cap to a gear oil squeeze bottle. I don't think I ever changed that, but I may have

 

I checked the front diff and it seemed a little overfilled. 30k change recommended, so I did. The oil that came out was cleanish, I'm letting it settle overnight to see if sparkles settle.

 

It scares me when the noise happens, I can feel the grind in the brake pedal,  but it self-corrects every time.

 

I replaced the front right wheel bearing, that seemed "maybe" a little notchy. I have seen much worse. I also replaced the left front balljoint which was a surprise that it was loose.

 

It was fine for a few days, but then the grinding showed up again, and again the brakes ground like crazy. It always occurs at highway speeds, without even touching the brakes, starting gradually, and building up to sounding like a wheel bearing failing. I pull off an exit, make a few turns, maybe it's cooling down, but then the sound is gone.

 

This is really ticking me off. Could it be an axle? How would the brakes interact with an axle?

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examine the brake pads - inner and outer - for 2 issues; are they very close to the same thickness?, and are they worn at an angle, wedge shaped? I'd also look at the edge of the rotor and areas of the caliper near the rotor and backing plate, etc. look for fresh metal/worn areas.

 

you might also consider taking some temp measurements of the hubs with an infrared thermometer after some highway runs. See if one side is consistently 30-40 degs or more warmer than the other side.

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examine the brake pads - inner and outer - for 2 issues; are they very close to the same thickness?, and are they worn at an angle, wedge shaped? I'd also look at the edge of the rotor and areas of the caliper near the rotor and backing plate, etc. look for fresh metal/worn areas.

 

you might also consider taking some temp measurements of the hubs with an infrared thermometer after some highway runs. See if one side is consistently 30-40 degs or more warmer than the other side.

 

I just had the caliper off when I changed the wheel bearing. All looks ok.  

 

It's intermittant, and only occurs on the expressway. I haven't touched the brakes in 10 miles. As soon as I turn off and exit, which means slowing down and making some turns, it seems to correct itself. I can only tell once I am back on the expressway. I suppose the booster could be pushing the pads, but that woudl be weird.

 

I think I've got a bad ball in one of the cages, frankly. I noticed when I press on to my destination within a few miles, I notice a hot rubber smell outside the car when I stop.

 

I stopped at Napa last night to just buy an axle; strangest thing. $67 for a Cardone, with an $84 core charge. They must REALLY want my OEM axle.

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I found the solution. It was the wheel bearing on the other side. This car is relatively new and tight enough that I couldn't tell what side was causing the problem.

 

See thread:

http://www.ultimatesubaru.org/forum/topic/151227-intermittent-rumble-fixed-undiagnosable-wheel-bearing/

 

"2008 Forester 85k miles. I had an intermittent serious rumble, from
the front end, that would occur typically after 10-15 minutes of highway
driving at ~70mph. The brakes also vibrated badly when it happenned. It
occurred about a dozen times over the past 3 months, unrelated to
anything like braking, turning, changes in speed, road surface. It would
self correct if I slowed or stopped for a few minutes. I checked both
front knuckles, going so far as removing the axles to check for bearing
play, but there was none. Even when I removed this the bearing

in the hub felt a-ok. It was only when it was pressed out (and broken
into separate races and rollers) that I could see this discoloration
that indicated overheating. The races show less discoloration, hardly
detectable. The races are heatsunk to the axle and hubs so that makes
sense, that they would stay cooler.


 


Here is what the bearing looked like:


 

sml_gallery_6836_515_75931.jpg

 

I dipped it in thinner and wiped it off. The brown discoloration of the rollers is in the metal, does not scrape off.

 

This bearing felt fine. It was impossible to diagnose; only by
disassembly (and destruction). When the axle was removed the bearing
felt completely smooth. The hubs never felt hot, or even warm, to my
hand, when I would pull off the road and check underneath when the
rumble occurred.


 


I guess I will go back to regarding Subaru wheel bearings as maintenance replace items, good for 75k only.


A google search of "intermittent rumble subaru" turns up a bunch of similar complaints.


 


This has stressed me out for a while. Glad it's fixed."

Edited by uniberp

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