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Discussion Starter · #1 · (Edited)
Ok I know 9/10 of you are wondering why there is yet another post on a rear end clunk. Well I have actually read many many threads on this and I'm still out of ideas.

BACKGROUND:

2001 BMW 330Ci

There IS a diff cluck and I do need to change those bushings. However, this can easily be reproduced by getting on and off the throttle quickly.

Additionally, I refreshed the rear end with new inner bushings, outer ball joints, Poly RTAB, H&R Race Springs, Bilstein B8 Sport shocks, shock mounts, and reinforcement plates.

I did have a 4 wheel alignment after all the work was done.

I inspected the subframe while I was under there and it looks fine and couldn't see any cracks.

Diff has Red Line oil as of this past March and brakes were done at the same time.

SYMPTOMS:

So the hard part about this is that it seems very random. Anything based on the drive line seems to have no correlation. Accelerating and decelerating will not produce the cluck.

Applying the brakes with various amounts of force also does not seem to be associated and braking is solid and balanced.

Now while driving I get a cluck and I have a hard time determining which side it may be on. Almost feels like it might be both but I notice it more towards the drivers side. Of course, I am riding on that side of the car so maybe that is biased. I have driven in a slalom, various left and right turns both fast and slow, and hit an assortment of bumps on both tires. Best thing I can say is that sometimes makes the cluck and sometimes not. Oddly, I can also hear it on what seems like a relatively smooth road. I don't seem to notice it at highway speed but there is quite a bit more road noise at the time.

I have bounced the rear end by hand while in the driveway and can't produce the noise.

Now I did have a front sway bar like get loose in the past and it seemed to have a similar noise and similar randomness. The rear links are only bolted at the upper control arm and while the springs were out I made sure to get these nice and tight.

So I am at a loss here. Like I said it feels nice and firm, just annoying and having done a lot of work to refresh it, I don't just want to attribute it to being an old car. What I hope is that someone may have done similar work and uncovered a similar issue or offer some theory that gives me that ah ha moment.

Thanks for taking the time to read!
 

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At a minimum, replace the rear diff bushing and two front diff bolts with the revised 10.9 grade part. New diff bushings are going to wear out your old subframe bushes faster so replace those too.
 

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Discussion Starter · #5 ·
I agree that diff and subframe bushings are due. However, the clunk is not the same as what I can produce through the diff with throttle. And I expect subframe bushings would produce the clunk through turns like in slalom driving.

Has anyone had issues with rear end links? It seems those could have the most potential.
 

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Do you have OEM rear swaybar endlinks? Maybe those have worn out? Both ends are tight? Did you check the bushing bracket on the sway bar was tight on to the body of the car?
 

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I would expected the clunking due to accelerating and letting go of the gas pedal would perhaps may actually be the cv joints aka axles. Perhaps the inconsistent one is the differential bushings
 

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Discussion Starter · #9 ·
All good replies. I am going to double check the end links next. They are new but it seems like it might be the most likely. Thanks to nleeumd for reminding me of the sway bar mounts themselves, that is really easy to check. I doubt it's the cv joints on the half-shafts since I can spin the wheels on jack stands and there is no clunk, slop, or binding. The diff mounts are definitely worn but I was pretty certain I could reproduce that noise since it's pretty well documented in many threads. However, it could be the front bushings that are moving while driving vs. the rear bushing that takes the punishment during acceleration. I am going to add that to the theory list and may be the next component to change if the sway bar links don't end up being the issue.
 

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Guys,

For anyone looking to upgrade to those bolts, I'll be making some side-notes on this thread as for the correct part # for people upgrading these bushings or replacing from stock.

My idea is to do the 2 front OEM and the Rear Diff using Meyle HD then do all Subframe Bushings while the mech is in there.
I also believe Giubo and tranny mounts are a must.

Can anyone else think of anything else that could cause these clunks that me or OP are missing?

I'm going to ask ECS tuning (via chat) if those 10.9 bolts are universal to the updated part # seen here:
https://www.ecstuning.com/ES56751/

33176760337

& reply with an update.
 

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I just did a major suspension refresh, front struts, rear shocks, springs, FCAB, RTAB, Rear Balljoints, Endlinks, Swaybar Bushings, etc. I am wanting to tackle the rear subframe bushings and diff. Would it make sense to buy a used e46 rear axle subframe and remove and press new bushings into the used one, so I can save time when i take out the one in my car?

Thoughts?
 

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OP...the clunk could be the CSB. The rear diff bushing is often said to be responsible for a clunk, too, but I believe it's probably the CSB.

That's assuming, though, that you've checked your subframe and have no issues with it. Of course, it could be something else, but this is among the most common clunking causes.

Replace the flex disk coupling while doing it...and be careful with this too...if you're off on coupling by one hole, you'll be off by a mile.

hth
 

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Had mine checked yesterday and it's the diff horizontal bushing......The tech showed me the bushing and how it was moving a good 1/4" plus.
 

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Discussion Starter · #14 ·
Well I wanted to follow-up and post the fix. Since the I knew the diff bushings were worn, I decided to replace those and it actually did eliminate the random clunk. Of course the clunk on acceleration is also gone, but that was to be expected. My guess is that it may have been the front diff bushings causing the noise while going over uneven surfaces due to the half shafts moving the diff due to the wheel travel. It was good to have that noise eliminated before taking the car to Summit Point for a PDX. Thanks to all that posted replies!
 
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