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2011 Edge Limited - thrumming noise 108K miles (audio included)

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I've been getting a thum-thum type noise that corresponds to wheel speed for about 2 years. It seems to be coming from the rear. At first I thought it was an out of round tire from the type of noise it made. I rotated tires making no difference. I've checked wheel bearings both manually and by doing side-to-side turns at 30 mph (noise is most easily heard at that speed). No luck. 

 

I put the car up on jackstands took off the tires and disabled the anti-lock brakes by pulling the fuse (must do this otherwise they try to engage) and had a friend accelerate to 30mph whil I circled the car with a steel rod to my ear to probe suspected spots. He could hear it but I couldn't isolate it to front or rear.  Too much other noise. The front right axle looked like it was wobbling a little so I replaced it and the wheel bearing since I had it and was in there. No luck. Noise is the same.

 

Since it felt like it was coming the right rear when I drive it, I replaced that wheel bearing - very rusted-in but found a neat trick of pushing out a stud and using another bolt to press against the knuckle finally worked.  However, that didn't fix the problem either.

 

I built a chassisEAR clip from a surplus peizo transducer glued to a battery clip. I plugged it into my phone's audio jack and used the voice recorder app to collect the sound. Since it was a single microphone clip I made multiple runs attached in different places including the front left wheel knuckle, the PTU, the transmission, the left and right rear wheel knuckles and lower arms plus 2 different spots on the rear diff casing. I ran each audio clip through audacity low pass filter of 300 HZ.

 

The noise was the most prominent at the right rear wheel knuckle although I can hear it in the left rear knuckle too. It's even less audible in the differential. The interesting thing is that I have a new hub and bearing in the right rear and the noise didn't change when I replaced it. 

 

Yesterday, I reached up and grabbed the rear axles. I could move the axle middle part from side to side about a 1/4" and it emits a soft clunk when I reach either the inner CV or outer CV joint. Both act the same. I grasped the CV housing near the diff and I find I can wiggle them a bit. I made sure there is nice clean fluid in the diff and there are no leaks.

 

I've attached a sound file from the right rear knuckle clamp microphone filtered to 300 Hz to eliminate  unwanted frequencies.

 

My questions are - does anyone have an idea what this could be? I'm worried that the bearing for the axle may be failing in the differential but can't find how to replace them. Does anyone know about these rear diff units that can shed some light on this issue? Any other ideas welcome.

 

Thanks in advance.

RtRear_knuckle.mp3

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How are the tires? (Brand, milage). I had a Sable with Michelin tires where the soft rubber wore off due to milage (20,000-25,000 miles) and had a sound simular due to hard rubber (which they use to get their 50k rating). 

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It's a good thought. @enigma-2 My tires are Cooper RTS (Formerly CTS) with about 9/32" or more tread and look like new. I've also rotated them with no appreciable difference in noise level. I don't drive that much so these tires probably have less than 20K mi on them. The noise has been going on for 2 years or so. I had to replace one of the rear tires last year when I ran over a garden rake that fell in my garage. The tire was like new and it broke my heart. Again, no change in noise.

 

I've replaced 3 out of four wheel bearings. The last change was front left and when I took off the knuckle and rotated the hub, I was surprise at how noisy it was. Unfortunately my chassisEAR mic didn't pick up anything out of the ordinary. And true to that finding, the noise is still there after replacing that bearing.

 

My next thought is to just replace the rear drivers sde bearing since I didn't hear the front bearing noises, maybe it will turn out to be the source. Only another $100 to find out (and 3 hours of separating the old rusty one).  I've been putting in Timken bearings rather than the $50 ebay knockoffs.

 

Thanks for the reply.

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hope you don't live in a rust belt state. if you do, expect a helluva fight getting the old one out.

 

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2 hours ago, WWWPerfA_ZN0W said:

hope you don't live in a rust belt state. if you do, expect a helluva fight getting the old one out.

 

 

I do live in a rustbelt state - Massachusetts - and the bearing looked like yours when I pulled it out. It took 15 minutes to get the bearing out once I got the 4 main bolts off that hiold it on. The secret, for those who don't know is using what I call the "bolt press" technique.

 

Cut off one of the lug bolts about 1/4" from the hub and push it through - hammer it through actually.

Remove one of the backing plate screws (I used the one on top) by using a 1/4" drive 8 mm socket on a small extension after aligning the missing lug hole over it. The 1/4" socket fits neatly thru the hole and the bolt removes with only a little persuasion.

Place a small piece of metal over the backing plate hole that is left and push a 1/2" x 3" bolt through the lug hole, thread on a nut under the hub, and hand tighten until the bolt is wedged between the small piece of metal (resting on the backing plate to protect it) and the hub. Start turning the bolt which will press the hub outward.

When it first starts to open, hit the hub on the opposite side with a hammer then continue to tighten the bolt.

Do this a few times and the bearing will be out before you realize it. I saw this technique here 

 

 

When I did the other side 3 months ago, it was taking me a half a day and still made no progress - slide hammer and all. After I saw the video, it was out in 10 minutes. This trick really works!

 

Now back to my original issue - the noise is still there. I've replaced all 4 wheel bearings (the last two were a bit noisy), and one front axle. I don't know if the center bearing in the drive shaft would "thrum" in time with wheel rotation, but I'll inspect it closer next.

 

What else could b making the noise - all ideas welcome.

 

 

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May not be worth the effort, but have you tried pulling the codes?

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I've looked for codes using Forscan and also a different OBD blue-tooth app. I didn't find any.

The weirdest thing I found so far was pulling off the right rear bearing (which I replaced 3 months ago) and it has a small bit of noise in it. I put in a Timken bearing thinking it's one of the best, but I used my "chassisEar" type microphone pickup on that wheel knuckle and that's where I hear the most noise from. Given that the noise was there before and after replacing it, I don't think it is the bearing again, but I'm really scratching my head over this.

 

That brake caliper was replaced because the original one failed but I can't remember if it was coincident with the noise starting. I checked out the caliper when I pulled the bearing yesterday and it still looks and operated like new. so I'm eliminating it as a suspect.

I also hung the mic on the center bearing in the driveshaft but did not hear anything noteworthy. The driveshaft feels tight but I'll go at it again with a pry bar to see if there is any play in the universals. I'll also change the PTU fluid while I'm under there. I changed it about 15k miles ago and it was pretty gunked up but now it seems to be more fluid and maybe I can get more old gunk out with this change. If the sound changes at all, I'll suspect the PTU even though I can't hear it on the mic.

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UPDATE: I went to the ford dealer for diagnosis. They said it is the intermediate shaft bearing and since the PTU had oil stains on it, they want to replace the PTU as well. Four years ago, the PTU pushed out the black goo from the vent and made a mess under there. I cleaned up the spots in the garage, then did a drain and fill. There was a lot of pasty sludge and eventually the suction hose got clogged. I was able to put about 4-5 ounces in after that. I've been driving since then with no leaks. 

I put chassis ears on the PTU and didn't really hear anything abnormal, but I never put it on the intermediate shaft bearing. 

The dealer quoted me $3,100 to change the PTU and intermediate shaft. Two years ago, the same dealer quoted me $1600 for the PTU. So I went to my local mechanic who also gave me a quote of $1450 back then. He told me to check with Ford again because they extended the warranty and I may be covered. I went back to Ford and they said it was by VIN only and my car wasn't on the list. 

I suspect that it is only the intermediate shaft bearing but the dealer wants to change the PTU anyway. But since my local quy told me it would be around $1400 still, I'll probably just do it so I can stop worrying about it.

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Make him lock the price in. (Guarantee not to exceed. Make certain he verifies that he can actually get a replacement as parts are on backorder and dealers get first dibs).

 

Its difficult to believe that the price is so close to where it was a year ago (due to inflation. Considering labor alone ...).

 

Also get it in writing that they are replacing with a new unit, not rebuilt and of the new design. (Ford has replaced the original design with one that has better seals and bearing. Still no drain however).

 

If the center bearing needs replacing, are you doing at the same time? 

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Thanks @enigma-2

When I took the driveshaft to the driveline shop, they told me that you can't separate the two halves of the driveshaft on this car as they are welded after the center bearing is put on. There is no bolt to hold the two halves together. Luckily, the rubber and bearing are good at this time because they said I'd have to replace the driveshaft if it goes.

 

The $1400 was an off-the cuff estimate. He says he does a lot of these but I will be getting a formal quote later in the week. He said he uses nothing but Ford parts but I will ask about new versus rebuilt. I don't think Ford deals in rebuilt parts but could be mistaken.

 

I can't believe it is in the front intermediate shaft because it seems very clear it is coming from the rear. 

 

I'll update when I know more.

 

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Latest:

Local mechanic will do it for $2200. He's done a lot of them he says.Unfortunately, He charges Ford list price for the parts ($1250 for PTU and $190 for intermediate shaft) when I could get them on-line for $900 and $128). But I know I don't want to do a job like this on the floor of my garage so I told him to go ahead.  It's $1100 less than ford and he does good work.

He has a caveat: 'as long as everything goes right since they have to remove the CAT and such. I already replaced the Y pipe 4 months ago so those should come off easily but the CAT to manifold and the O2 sensor I assume are the only real risks. Anything else?

 

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