Noise from rear end of an H6

6492 Views 15 Replies 6 Participants Last post by CNY_Dave, Feb 19, 2014

TrekLawler

Discussion Starter · Nov 20, 2012

Hello everyone,
I'm hoping I can tap into some Subaru experience here

. I have a 2001 Outback L.L. Bean with 260,000 miles on it. The car is absolutely in excellent shape and I've taken very good care of it mechanically. However it has recently developed a very odd noise from the rear differential that has me baffled.
Sometimes when you put it into reverse (and only in reverse) it gives a very loud clunking noise, almost gives you the impression that a CV or u joint on the drive shaft has gone bad, but these have been replaced in the last month, so have been ruled out. At other times if it doesn't clunk when putting it into reverse it will give the clunk as you're backing up. I've pretty much isolated it to the rear differential however can't imagine anything that could go bad which would only cause this to happen when the car is put into reverse, but am open to ideas and suggestions. Any thoughts would be appreciated. :help:

Thanks,

1 - 16 of 16 Posts

1 Lucky Texan

· #2 · Nov 20, 2012

could you listen back there outside the car while someone else backs it up? See if the sound is at a wheel or more central.

could be something with a brake pad/caliper or the parking brake parts inside the rotor.

also, there are bushings at the differential mount that could be destroyed. control arm bushings too.

You said the ujoint was OK, there's also a carrier bearing. dunno if it could clunk though.

at that mileage - I suppose a rear CV joint could be bad.

TrekLawler

Discussion Starter · #3 · Nov 20, 2012

Thanks Lucky Texan,
Both half shafts have been replaced with new CV's so I'm hoping that isn't a problem :gasp:. It's definately more central, I haven't been able to stand outside of it when someone else is in it however have hung out of the car in an open parking lot and can hear it, it sounds like metal on metal since it's a clanging noise (if that makes sense) almost like the front wheels were engaging and then as the car was rolling backwards the rear was unloaded and then caught up and the pinion gear hits the ring gear.
I thought about the brakes as well however the car freely rolls backwards when put into gear and the noise will not present itself until you give it some gas (if it doesn't clunk going into gear).

One thing I forgot to add is it doesn't do it all the time, sorry.

Thanks for the thoughts though, you've given me a couple of other items to look into with the bushings as I'll check them.

CNY_Dave

· #4 · Nov 20, 2012

Was the driveshaft fully serviced or just one or two u-joints replaced? The rubber mount for the carrier bearing could be shot.

The rear trans mount might need new rubber bushings, ditto the rear diff.

cardoc

· #5 · Nov 21, 2012

https://www.youtube.com/watch?v=PhiPClMZG1s&feature=plcp

And the fix for now so I don't have to remove the diff carrier was to remove the skid plate, clean the bushings with brake cleaner, inject 3M Window Weld into the gaps, let it set for the afternoon and over night. The following was the result. The body and suspension moves, not the diff.

https://www.youtube.com/watch?NR=1&v=B15Uji_QXR8&feature=endscreen

Its funny every time I see it.

,

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TrekLawler

Discussion Starter · #6 · Nov 21, 2012

CNY_Dave said:
Was the driveshaft fully serviced or just one or two u-joints replaced? The rubber mount for the carrier bearing could be shot.

The rear trans mount might need new rubber bushings, ditto the rear diff.

Thanks Dave,
both U joints were replaced as one of them was pretty stiff and grinding a bit. The rubber mount on the carrier bearing was checked out and looked OK with very little movement. My first thought was it was a U joint as that is what it sounded like.

Thanks,

TrekLawler

Discussion Starter · #7 · Nov 21, 2012

Thanks Cardoc,
My son and I are going to go out this afternoon and check these out. When I removed the differential just about two weeks ago to replace the half shafts and CV joints the rear diff bushings looked very solid as they supported the diff when I removed the front mount.

But I've seen weirder things.

Thanks for the feedback.

03LLBean

· #8 · Dec 15, 2013

cardoc said:
https://www.youtube.com/watch?v=PhiPClMZG1s&feature=plcp

And the fix for now so I don't have to remove the diff carrier was to remove the skid plate, clean the bushings with brake cleaner, inject 3M Window Weld into the gaps, let it set for the afternoon and over night. The following was the result. The body and suspension moves, not the diff.

https://www.youtube.com/watch?NR=1&v=B15Uji_QXR8&feature=endscreen

Its funny every time I see it.

,

Hello all,
My family's 2003 recently started having the problem outlined in this thread.
I inspected the rear end thoroughly today and the diff bushings all felt quite solid. Is it possible that the high stress low speed situation (more details in my thread) could be causing problems with the diff bushings, which go back to normal as they cool off?
Thanks,
Alex

03LLBean

· #9 · Dec 15, 2013 (Edited)

Cardoc? Trek Lawler? Anyone?
I imagine this will be quite difficult to diagnose as it only makes the sound right after slowly reversing up a hill or driving up a hill.

avk

· #10 · Dec 15, 2013

Make sure that a rusted-out rear subframe has been eliminated as a cause the noise.There would be noise if it gave way and made metal-to-metal contact with the body structure.

03LLBean

· #11 · Dec 15, 2013

Thanks. In my inspection yesterday the subframe looked fine but I'll double check.

cardoc

· #12 · Dec 16, 2013

Did you look at the bushings while someone was inside the car shifting the transmission from R to D? The torque from the drivetrain will move it more than you can by hand.

03LLBean

· #13 · Dec 16, 2013

Avk, I checked the subframe again today. It's quite solid.
Cardoc, thanks. I'll make sure to try that.
There's been some more discussion in the thread I linked.
Edit: I just got an idea.
The next time the car has this problem, I'll climb under it and have someone shift from neutral into reverse. If the diff doesn't move, I can rule out bushings right?
How much movement is ok?

cardoc

· #14 · Dec 16, 2013

Not much.

Another thing that could be making the noise is the rear driveshaft or differential. Its difficult determining a noise over the internet. A recording when it does it may help.

03LLBean

· #15 · Feb 18, 2014

I never did get a recording. The car hasn't made the noise since I first posted.
As I mentioned, it's been making the noise on and off for years, and now that I'm trying to record it, it's taking a break.

CNY_Dave

· #16 · Feb 19, 2014

Perhaps it is cold enough some weak bushings have stiffened enough to prevent the clunk.

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