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e46 & e30 baur
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Discussion Starter · #1 ·
I've had a small clunk from the rear end and it's gradually gotten worse to it now sounding like a socket is rolling around in my trunk all the time (there isn't one). Another sound is related to the rear wheel speed when everything is cold but I think that's a diff bushing. Car sounds just fine at highway speeds with no concerning sounds above 45mpg. I ordered all the bushings to do a rear end refresh, but I'm reading a lot about the subframe mount cracks, how likely is a 2004 car to have them? Was there a model year that they started doing structural foam or is that a DIY fix I could do if it's not cracked? If it is cracked I'm planning on finding someone to weld in the Turner Motorsport kit since it seems to be the most affordable and simplest.

It's a manual 325i sedan and I'm pretty sure it wasn't beat on that hard its first 180k miles of life. The meanest I get to it is snow drifting it now and then. It still has the clutch delay value which means it hopefully has had that safety net keeping the chassis safe. Car alignment is still good and doesn't change when bumps are hit and the wheels don't seem to move when pushed but the rear right makes a springy sound when smacked.
Any help is appreciated!
 

· OEM ///PLUS
2003 M3 6MT Slicktop
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26,371 Posts
it could be a cracked rear axle carrier panel (RACP) which is often improperly referred to as “subframe”.
it could also be a number of things like a broken dead coil in a rear spring or even broken rear shock mount. you’ll need to get under and examine.

BMW didn’t do the epoxy foam from the facotry. it was a later fix for some smaller cracks during the voluntary recall inspection around 2009-2010. so yes, if your car had small cracks and was inspected then BMW could have done the epoxy foam.
 

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2002 325xi
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Ha!
 

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2001 325ci
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Get under the differential and look up to the floor to see any crack lines near the subframe 4 mounting points.
it could be a cracked rear axle carrier panel (RACP) which is often improperly referred to as “subframe”.
hasn't paid attention to this problem...for my 325
would any M54 3.0 susceptible to this?
 

· OEM ///PLUS
2003 M3 6MT Slicktop
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hasn't paid attention to this problem...for my 325
would any M54 3.0 susceptible to this?
yes. earlier pre 2/2000 builds the most.
 
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e46 & e30 baur
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Discussion Starter · #10 ·
I was messing around last night a bit on the way to the store and my diff bushing is also bad in addition to the other high frequency clunk noise.
When I get home I'm going to do the bushings, and if the subframe mount or anything is cracked I'll revaluate. As a control I'm going to pull the entire trunk interior out and inspect those shock mounts too!
 

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2001 M3
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Surprisingly I had 8 cracks in a 140,000 mile M3. Installed (welded) the kit, now, tight as drum. Diff bushings are a problem and can fail from age alone (no beating required). Also check the driveshaft CV joint, it gets no love and makes lots and lots of revs during it's life. My theory, take it apart once and fix it all, you will be rewarded.
 

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Discussion Starter · #12 ·

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2001 M3
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2001 M3
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I bought the BimmerWorld one but I am sure the Turner one is good to. The pieces are surprisingly
light so prep and quality welding is key. Take your time on these or whoever does it. Don't forget to
paint when done.
 

· OEM ///PLUS
2003 M3 6MT Slicktop
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26,371 Posts
Subframe is out! Mounts are not cracked, should I epoxy them for the faster turn around or weld them anyway
hard to say. there’s three ways I see of approaching this and all three fit a different want/need…
1) do nothing. car likely lasts it’s user “lifetime” never needing it. save time/money but never being positive it’s not going to be an issue later.
2) epoxy foam. some peace of mind, not a lot of work/money. but not knowing if crack in front right might happen or rust breach.
3) plates. peace of mind all four mounts are reinforced. also helps alleviate internal rust breach at mounting locations. more overkill, more money/time to have done. raises rear. will also need an alignment.
 

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2001 M3
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It all depends of what you are going to do with the car. Invariable one of the first questions from a buyer will be the condition of the rear subframe followed by rod bearings, oil pump nut. Could very well last the time you have the car and it can be done later when maybe cash is not so much of a hurdle.
 

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325i Touring
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148 Posts
I would avoid epoxy for fixing reinforcement plates. Silly half-arsed solution. If you're going to put in all the effort, might as well do it properly.
If you really want to make the car future-proof, you're best to also do topside reinforcement in addition to the bottom reinforcement plates. That would involve cutting up the boot floor and at the very least adding in weld plates that connect the RACP to the chassis rails. If you want to take it a step further, also add the weld in beam that connects the chassis rails for extra rigidity. Also, no plates are required there per se, but it's worth doing additional stitch welds around the trailing arm pockets.
No affiliation, but CMP Auto Engineering ones are what I'm going with for my Touring. Even if you're going with some other brand ones, their tech articles are a must-read to get a good idea of the nature of the issue. Most comprehensive write-ups on it that I've found anyway.
 

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2003 M3 6MT Slicktop
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Invariable one of the first questions from a buyer will be the condition of the rear subframe followed by rod bearings, oil pump nut.
he doesn’t have an M3
 
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