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Hi everyone! I recently bought a 2004 325xi 5speed with 115k miles in it. A few days ago I started hearing a quick "thud thud". To me it sound like it is coming from the middle to back off the car in the passenger side. It'll do it either when I hit a bump just right with the back wheels, or when I downshift kinda of quickly. No sound or any drivability issue when upshifting or on smooth surfaces. My first thought was struts, but since been told it could possibly be diff mount or something like that. Any ideas? Thank in advance!
Fast
Could be the rear upper shock mount.
Member
Yeah that and the rear diff mount have been suggested to me. I'm working today so tomorrow I'm guna get under there and investigate. I'll post pics of whatever I find!
Fast
Solid plan.
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Mine has been making a slight thud in the rear passenger side when I hit uneven potholes and stuff only with that tire. I'm planning to replace the RTABS and ultimately subframe bushings to try to eliminate it, since my rear shocks are new.
Member
Ok, so I have it up on a lift as we speak and all the bushings( diff, subframe, control arm) seem good.the only thing I can find that's loose or has movement is the fuel tank. I'm thinking I could put a strip of rubber between the tank and the metal strap? Anyone else ever had a problem with that?
Fast
I do exactly that. I take a piece of 3/4 heater hose, cut it once lengthwise and wrap it around the strap.Originally Posted by Jasonn325xi
Such Membr
...scary.
Maybe also zip tie the rubber/hose into place? Keep it there until it can be properly remedied.
Fast
Every E46 I've owned has had a "loose" tank. Meaning there is movement up and down and side to side, even with the straps tightened all the way.... As far as I know, no parts have failed and there is no "proper" fix. Must be by design.
Last edited by dhurley34; 04-11-2016 at 12:10 PM.
Such Membr
Mine doesn't...
*runs to check car*
Fast
Check it with the tank low on fuel. If its full, it wont move due to weight.Mine doesn't...
*runs to check car*
Such Membr
I absolutely will.
I did inspect it 2 months ago when I pulled and refreshed my rear-end rubber (subframe and all). I took a good look at the strapping while I was under there relaxing my shoulder and noticed no play. Sagging metal due to loaded strain does make sense though, I'll have to wait a few days till my gas gets lower.
Member
Thanks for the very quick reply everyone! I'm going to wedge a strip of rubber between the two, go for a ride and listen very closely. Hopefully that will remedy the "thud" noise. I'll be back later to report if the problem was fixed!
Member
So I got the piece of rubber hose in there and I'm still hearing the thud. I think it might not be doing it quite as much but that could just be me tricking my own mind lol. I attached a pic of were I put the rubber.
Last edited by Jasonn325xi; 04-11-2016 at 06:37 PM.
Such Membr
Did you check your suspension components yet?
From what dhurley suggested I am inclined to think that if you can't deflect the tank in the same way, then it shouldn't make the same noise. Or at least not the same tone/volume.
Member
The coils and shock mounts seemed good, no play or anything. But the front shocks are newer looking bilstein shocks and rear shocks did look much older. The rears shocks are black, they almost seem like they could be factory, possibly? And I was thinking could a bad shock even cause a noise like this when down shifting quickly?
Last edited by Jasonn325xi; 04-11-2016 at 10:35 PM.
Member
And it's been doing it with a half full or completely full tank so that makes me think it isn't the gas tank, even though it sounds like it's coming right from the area of the tank. What else is even in that area on the passenger side?
Such Membr
I shudder to think the worst.
Have you done any inspection of the points where the rear sub-frame meets the body?
I have not heard of many (or any) Xi cars having this issue, but you never know until you look.
Have you had an alignment done yet?
I stand by what I have said before, the thud from shifting that I have experienced came from bad diff bushings..and they don't necessarily have to look bad in order for them to be bad. It is a commonly failed bushing, from what I'm told it's pretty common in manuals for them to go "quicker" due to...yano...manually shifting.
How did you check the diff bushings? If I may ask.
Last edited by Doge; 04-11-2016 at 10:47 PM.
Member
I just grabbed the diff and tried manhandling it see if it would move haha... and I looked at the bushings, they were "there" and making contact on both sides, and they didn't seem too dryed up. I have not had an alignment yet, though I probably should. Where are all the points were rear sub-frame meets body? I was able to look around pretty good and nothing looked out of the ordinary. Would I be looking for damage done to the body by the sub-frame?
Last edited by Jasonn325xi; 04-11-2016 at 11:54 PM.
I Void Warranties
IIRC the XI cars had reinforced subframe points from the factory. You have to really bash them to cause the subframe issue that's common on the coupes and some sedans.
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Yes, Basically you are looking for torn sheetmetal on the body where the subframe mounts go through.
Such Membr
That would be interesting if the Xi did have that reinforcement, you're totally right...Though, from the research I have done pre-2001 E46s and just about all M3s suffer this fate at a much higher frequency. For some reason the 323s specifically, the M3s make sense with the 100 extra ponies.
But I have not seen ANY reports of an Xi suffering this fate (not to say it couldn't happen of course).
The way I checked my diff bushing (rear only, since all three should be changed together) was to get a pry bar and deflect the diff while watching the bushing for too much deflection, separation from the metal sleeve, and dry rotting that would only show itself when the bushing deflects. Mine had a very obvious crack in the rubber and deflected a bit too much..plus I had a "thud/thump" noise whenever I dropped the clutch a bit too hard, and the noise very obviously came from the rear.
If you do the bushing job yourself you will need to purchase a specialty clamp rig (I made mine from bits and bobs from Home Depot, b/c the one I bought for pressing wouldn't fit).
Fast
The XI's do not have factory reinforced rear subframe points. XI's have factory installed reinforcement plates for the front strut towers. The reason why you don't see very many XI's with subframe damage is because the rear wheels only receive 68% of the engine's torque. Torsional loading of the rear subframe mounting points is what causes the damage. Particularly the rear drivers and passenger front mounts. The rocking back and forth weakens the rosette welds and eventually causes separation. Think of it as bending a piece of thin metal back and forth over and over, eventually it splits. Since RWD vehicles receive 100% of the engine's torque, they are much more susceptible to damage. XI's with damage are almost always neglected 330xi's. I have never even seen a 325xi with preliminary signs. But there is a first for everything. Subframe damage is sounds like a "click click". A thud could be a failed subframe bushing. Two completely different animals.
Last edited by dhurley34; 04-12-2016 at 11:43 AM.
Such Membr
Yeah, that's basically what I was thinking...only not so elegantly put
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Thank you for clarifying.
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