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clank/clunk from rear end

5K views 22 replies 10 participants last post by  Dazza335iC 
#1 · (Edited)
Hi all, I'm trying to locate the source of this very annoying clank/clunk in the rear of the car. It's very much a metal-on-metal type of sound, and from outside the car sounds sharp and metallic. It happens over even small bumps in the road, and is originating somewhere in the rear suspension. I've put the car up and checked everything I can think of multiple times. Bushings, heat shields, exhaust hangers, dust shields, lines, suspension components, etc. Everything looks and feels solid, I've shaken stuff and banged stuff with rubber mallets to no avail. :banghead:

I'm at my wits end trying to track this down and I can't find anything, so it's time to ask the interwebs.... Are there any parts of the rear suspension that are more susceptible to this? Or any known trouble spots for noise? Thanks for the help!

edit: I should also mention that it's pretty damn loud outside the car, and also audible inside but more muffled and quiet.
 
#2 ·
Have you checked the rear shock mounts?
 
#8 ·
I would check:
- Differential
- Rear Shock Mounts
- Rear Shocks themselves and rear A arms
- Subframe Mounting Areas
 
#9 ·
I just jacked my rear up tonight and twisted the wheel, the wheel moved left and right an inch, and each axle twisted and the diff moved around.

If I twisted fast enough, the diff actually lifted in its place. Do I have shot diff mounts or is this normal?
 
#10 · (Edited)
Got a chance to do some inspections yesterday:

RSMs look to be in good shape. I found the service history saying they were replaced about 20k ago with OEM pieces.
Auto part


Subframe looks good from both above and below with no signs of cracking or tearing
Auto part Metal Shoe

Red Automotive exterior Bumper Rim Vehicle


I did notice some cracking in the rear diff bushing but it's not what I'd call severe
Architecture Auto part Automotive wheel system Wheel Metal


I also pulled apart the brakes and e-brake on one side and found nothing of note. Everything looks excellent.

The only thing I noticed was a fair amount of play in the bushing that connects the UCA to the rear spindle. I'm not sure what the name for that bushing is, but the UCA had a lot of movement/play when I pushed on or twisted it, and it didn't take much force to move it around. Thoughts?

edit: just saw this in another thread:
...and i blew three sets of Meyle HD shock mounts on aftermarket dampers. one brand new pair after the other. They don't blow through completely, the bushing just gets warped to sh!t and the shock starts knocking
Maybe time to step up to aftermarket RSMs. I know Turner and Rogue make good stuff, any opinions on these or others?
 
#11 ·
Try removing your rear seat and lowering the top of the seat down. This will allow more noise to get through the cabin. Maybe this will help you pinpoint where the noise is coming from.
 
#12 ·
You may need to replace the rear inner upper and lower control arm bushing/bearing. I did w the TMS bits during my 325i overhaul, and the old ones were shot.

For the RSM's, I have typically gotten Rogue ones, zero problems.
 
#13 ·
After seeing the headaches involved in replacing those LCA bushings I may just order new lower arms. The uppers seem to be easier from what I read, as long as you have the right tool.

First step though it to put the seats down and crawl in to the back while the wife drives around, give the shock mounts a good looking over.
 
#14 ·
I have the same clank/clunk sound coming from the rear end. Checked all of the things you did and no luck.

Finally figured it out. Sounded like metal tools clanking together on a metal pan.

Turns out it was the metal clip/bar that holds the battery in the tray. Try lifting up your battery and slightly dropping it. I bet it's that sound.

Let us know what you find. It worked for me to tighten the clamp to the battery tray.
 
#15 · (Edited)
That's a good idea! I'll check it in the AM.

I put the seats down, crawled in the back and had my wife drive around for a few miles. I heard the sound very distinctly, louder from the passenger side but also from the driver side. It was not the shock mounts. It was definitely coming from underneath the trunk floor, near the rear wheel. Metal-on-metal clanking and rattling, like a bushing was completely shot perhaps? I've priced out a full set of bushings from Turner for the rear and it comes out to near $700 when you include new lower arms and aftermarket RSMs... not cheap, but owning a BMW never is :/

I'll keep trying to hunt it down before I blow that much money and a whole weekend trying to fix it though. Anyne have a rear bushing tool set they're willing to loan? :)
 
#17 · (Edited)
The battery clamp was a bit loose, but it wasn't the source of the sounds.

I did notice though that the sound goes away whenever I apply the brakes. Like I said earlier I pulled the rear brakes apart and checked everything, I don't think that's the source. Maybe it's the force they exert on some loose suspension parts back there.

I ended up ordering all new RSMs, RTABs, upper and lower outer TABs and lower arms with inner bushings. The price through blunttech was about $200 less than Turner, and better quality. I'll also have to replace the diff bushing at some point, but I'd like to avoid it for now.
 
#20 ·
I drove it to work this morning and so far it seems (knock on wood) to be fixed. But I don't want to say for sure yet because I didn't go over any bumpy or rough sections of road. It goes in for an alignment this afternoon, and I may ask the shop (Pacific Motorsports here in Portland, they specialize in BMWs) to take a look for anything I may have overlooked if the noise is still there. At this point I'd rather pay for an hour of diagnostic time than continue to throw more parts/time/money at an unidentified culprit.
 
#21 ·
Problem: Solved (and it's not what you think...)

So after taking the car to Pacific Motorsports for an alignment (and discovering that with the H&R Cup Kit the breakover angle was too low to get on to their rack) I started chatting with a freind of mine who used to be a mechanic at the local BMW dealer and now works there. I described the noise to him and he offered to go for a quick test drive around the block.

Immediately upon pulling out of the lot and hearing the noise, his comment was, "does it make the noise when you're applying brake pressure?" I didn't know, but a quick drag of the brakes revealed that yes, the noise stops when the brakes are applied. His diagnosis was that the 3-prong retaining clips on the inner brake pads (the prongs that fit in to the I.D. of the piston) were loose and allowing the pad to shift and rattle in the caliper. When braking force is applied the pressure prevents the pad from shifting, hence no more noise.

So long story short, the rear suspension clank/clunk was actually caused by loose inner brake pad retaining springs. Once I pulled the pads, spread the prongs to increase clamping force and re-installed everything, the noise was completely gone. I hope this helps anyone else trying to track down similar issues!

 
#22 ·
I have same noise tried to take rear passenger tire off cause that's were the noise came from but it won't come off its if it was stuck unto the hub I shaked control arms and shocks which I recently replaced but then I notice the rear passenger tire was twisted like the tire wasn't straight help please what could it be

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