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Discussion Starter #1
Hi All -- I have a 2001 manual E39 530i with 130K well serviced miles. I get road noise from the rear that sounds like driving over rumble strips at times. The noise varies according to road surface but is always there to some degree. It also varies with car speed -- and is there when coasting also. Before taking things apart, I'm guessing the three most likely causes are: tyres, bearings, rear diff. Anyone any idea which is most likely based on symptoms? There are no other symptoms - vibration etc. The car drives superbly, but with this noise. Thanks in advance
 

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Difficult to say - but from your description, I'd be thinking about wheels out of true/wheels out of balance/tyres as first port of call. Fortunately, that's the easiest to rule out as you can swap them from the back to the front and see if the noise moves with them. And if the noise does move, swap one wheel at a time for the spare to nail your culprit.

Some other contenders to your list would be worn mounts/bushes at the rear - diff mounts/sub frame carrier/Rear trailing arms - play in any of those could exacerbate noise and vibrations.
 

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Discussion Starter #3
Thanks very much for this. Is the diff itself the least likely? Obviously that's a concern given it's most likely to be the costliest to fix?
 

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I certainly wouldn't be worrying about the diff until wheels/tyres/balance has been ruled out. The diffs are pretty robust but they can sometimes give out - I had one go at 28k on my 6er so it's not unheard of, but my 330d is ploughing through 200k on the original diff (touch wood). The fact that your noise is varying with road surface would tend to point away from the diff so fingers crossed!
 

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Discussion Starter #5
Cheers -- my experience with diffs on other cars is that there are other symptoms: vibration, clunks etc etc, so hopefully it is wheels or tyres.
 

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Yeah - if the tyre is out of round or if you've got really bad saw tooth wear, it's quite possible.
 

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I'm not sure (as in I don't know I'm afraid)... have you tried swapping rear wheels to the front to see if the noise moves forwards?
 

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Discussion Starter #11
changed tires. No difference. Checked rear wheel bearings. Both smooth. What now? Tire fitter commented that brake discs had high spots. Not sure whether that was to sell me new discs or not. Could that cause the noise I'm describing?
 

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Theoretically yes - although its not something I've come across personally. Could try getting the discs skimmed - or do some serious braking from motorway speeds a few times to see if it makes a difference?
 

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Thinking about this it could be a warped wheel rim. One of my 535is I know has at least one slightly buckled rim (given the potholes around here it isn't surprising) and it has more rolling noise than the other one. It is difficult to pin down without hearing the noise and being able to get a sense of the source. Prop shaft bearing is another possibility. If you could get it up on a lift and get under it with the wheels turning you might be able to narrow things down a bit.
 

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You need to check the alignment but before doing that lift each side and check the wheel for play holding the tyre at 3/9 o'clock and 12/6 o'clock respectively. Shake the wheel and if you notice any play you need to replace what's worn. Only then do the alignment. Also make sure the alignment values used are for an SE not Sports which has more agressive toe in values eating the tyres on the inside.
 

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If you have slight hum in the diff add Liqui Moly Ceratec, and of course make sure it's topped up with oil.

Wheel bearing noise - firstly the noise it makes is horrendous; you would think the wheel is about to fall off (it won't) and the tune changes with cornering as weight shifts from side to side.
 
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