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Discussion Starter #1 (Edited)
I have a noise that I think has been developing for the last 10000 kms that i need help diagnosing. Until yesterday I thought it was one of my front wheel bearings. In the midst of the noise developing I have replaced all 4 wheel bearings. The wheel bearings in the rear went about 6000 km and 3 months apart and I let each of them deteriorate until they had significant play. Since this noise at the front sounded similar to the wheel bearings in the rear i picked up the front wheel bearings and changed them yesterday. The front bearings didn't have any noticeable play but inspecting them after removal I'm sure one of them was actually on its way out very soon.

Noise description:
1) Happens under acceleration (Light acceleration/hill = light noise; spool the turbo or big hill = more noise; noise is very proportional to torque)
2) The noise sounds like a bit of a whirring tire rub; increases in speed with the tires and only whirs over say 25% of the rotation.
3) Starts around 15 km/hr and is loudest around 58 km/hr then settles down at highway speeds
4) I struggle to tell if it is central/right/or left but it definitely is front end and probably right
5) If i pop the transmission in neutral it stops (removed load)
6) No vibration with the noise (as of today)
7) It didn't change from anything I did yesterday
8) No low speed noise (under 10 km/hr ish)
9) No clicking turning tight in parking lots etc.
10) 2nd gear or 3rd gear or 4th gear makes no difference. Torque is torque.
11) UPDATE: driving now I notice the noise stops when I touch the brakes. I'll be taking those apart right away to see if this isn't much simpler than first appearing.

Observations from my inspection this morning:

After doing a bunch of reading last night on the forums I went out this morning to take a good look at the right and left half shafts and the prop shaft to the rear. I was expecting to find play or noise in the right half shaft carrier bearing or something but most everything looked and sounded perfect. I had the car safely jacked and was able to turn the wheels while I was under there.

Right half shaft:
-Top of brake shielding was rubbing the brake rotor at the start and I bent it back out of the way (Dropped the rotation noise to almost silent..speaks well of yesterday's bearing install)
-Perfectly snug at the angle gear
-Perfectly snug at the half shaft carrier bearing
-Ever so faint squeak at one part of the rotation which i believe is just some brake pad drag (Maybe I should stethoscope this carrier bearing?)
-Grabbing the shaft by the angle gear and the tire and moving the tire back and forth no play that I could feel rotationally
-Grabbing the shaft by the angle gear shoving toward the angle gear or toward the carrier bearing felt as I would expect (no play or 1/32")

Angle gear:
-Healthy feel in direction change/backlash between half shafts and prop shaft (prop shaft is what I call the drive shaft to the rear)
-prop shaft turns with front tire
-light blackness on the exterior maybe from the turbo above (no seepage evident from the split line seal or half shafts or prop shaft or transmission. Looks like new)
-Angle gear coupling seems fine

Prop Shaft:
Front Prop Shaft CV Joint:
-No radial movement of the shaft
-Shaft feels snug and I can slide is back and forth ever so slightly (as constrained by the center prop joint bearing)
-No sound when turning the shaft

Center Prop Shaft Bearing:
-No radial movement (ie. when I push up on it feels perfect)
-No sound when turning the shaft

Rear Prop shaft CV:
-I didn't crawl all the way back there but did grab the shaft past the center bearing and it felt good. (I had the shaft out 14 months ago and I'm fairly confident in my bolt up back there)

Left Half Shaft (Shorty):
-At the tranny if I push up on the half shaft near where the spline enters the transmission I can move it up a little (like 1/16"). This surprises me when comparing against right side half shaft at the angle gear where there is zero play. This is how they feel on Subarus I've seen in the past.
-Rubber boots look fine but the inner is covered with black dust that was misted on there from some hydrocarbon source
-Outer boot looks perfect
-If I grab the rubber/plastic balancer looking piece at the center of the half shaft I can move the shaft in and out a little. Seems fine.
-I can't get any real clicking or play when I rotate the tire and hold the shaft. Connection seems positive.


Thoughts:
When I thought the noise was a wheel bearing i had no concerns about hard acceleration and driving the car. Now I don't know what I'm dealing with and if I should park it or take it to the dealer. I can get half shafts for under $200 each as opposed to an hour of dealer diagnosis time which usually costs about that.

Half shaft CV failures I've experienced on other cars usually come with clicking (outer cv) or vibration maybe for the inner cv....and this seems different. I've never had a car with a half shaft carrier bearing.

This car lives in Canada and from what I see everything seems to be in great shape compared to those that operate in really hot climates.


Probable:
1) A CV on either half shaft
2) Right half shaft carrier bearing
3) Prop shaft (but it seems perfect under the car)
4) Bearing in the transmission at the interface with the left half shaft (seems very unlikely)
5)???


Any help on this is appreciated. Any guidance on how to better check the health of the half shafts or haft shaft carrier bearing would be especially good. Any guidance on if I should be driving it or not is good too.

Recommendations?

Thank you.
 

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Discussion Starter #3
I had a look at the right front for closer inspection of that brake setup. The right front rotor is warped and I was able measure about 0.01" runout on each side using a dial gauge. This leads to a lot of drag in one spot as I turn the rotor through the caliper which is still very noticeable with the rim and tire mounted. At 110km/hr I can feel it in the steering wheel when I brake as well. I see some comments on line that even 0.001" runout can be felt in a car and this rotor is well beyond that.

I struggle to believe this noise (which really seems to be torque dependent) could be the result of a warped rotor. Coasting around town and downhill its practically not noticeable (but I think its rotor drag I hear starting around 30 km/hr) but it gets loud through 58 km/hr and even 4th gear and accelerating hard at 80 km/hr it sound like the chafe at a high rate of speed.

Maybe it is possible that there is enough natural slap in the wheel bearing that the rotor moves a bit and the noise gets amplified when on the gas? I'm running factory wheels and the correct tire size I would think they would put the wheel bearing generally over the center of the contact patch and there'd be no moment arm to twist the rotor toward the caliper. With wheel alignment comes a lot of variables so maybe not.

These are the 4 pot calipers and they are mounted super stiff.

Anyone seen anything like this?

Thank you.
 

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You can check the brake pad to rotor contact by pushing the pads all the way in so the pistons are in full bottom position. To do this you will have to put the vehicle in neutral before you start. Push the brake pistons on all wheels in so the pads are not touching rotors. Start vehicle and run your test again to see if you have the noise. If you still have the noise it is not rotor runout. Be careful because it could take you a few brake pumps to get full braking back. Glück.
 

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Discussion Starter #5
An update: I removed the prop shaft: Noise was gone; gambled on it being front prop shaft joint and got a great deal on a brand new prop shaft. New prop shaft works great, noise persists. Had the dealer run it on their stand. They believe the noise is in the angle gear but don't comment on potential causes. So I'm down to about three possibles: 1) angle gear coupling spline wear (that couple with the inner spline that brings torque from the tranny to the angle gear...relatively easy to change out) 2) bevel gear working on the spline on the main shaft within the angle gear (Yikes!); 3) bearings in the angle gear(meh).

I rate #3 as unlikely but we'll see. So far I seem to be making a plan to take the car off the road for a few weeks to dismantle the angle gear. I've seen lots of good posts online about breaking down the angle gear and rebuilding it...I've made some calls and I'm confident I can get bearings for it. If its problem #2 I'm yet to find threads from anyone showing they've had success with just welding up the bevel gear to the main shaft spline within the angle gear (I'll keep looking). Of course a key concern here is I dismantle the angle gear and find nothing obvious to address.

For now I pulled the fuse on my AWD system. This gives me a warning about stability control requiring service. But similar to removing the prop shaft it relieves the angle gear of torque and such eliminates the noise (and hopefully wear on the angle gear for now.) This saved me from pulling the prop shaft again.

FWD until further notice.

This thread would probably make more sense in the R forum afterall. Thank you.
 
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