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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Rumble/Vibration from the rear when WOT on a tune



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      11-07-2012, 01:26 PM   #1
KaiserN54
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Rumble/Vibration from the rear when WOT on a tune

Someone else asked a similar question in the forum Whose Name We Dare Not Speak ...


Does anyelse here get a subtle vibration and hum from the rear of their car when WOT in 4th, 5th, and 6th gear? (only when running a tune)

I have had this problem in both of my 6mt 335i's. The one I have now is on its third diff (first one replaced under warranty for whine, second one replaced with Wavetrac LSD) and it still does it. Some in the other forum suggested it could be something to do with the gap in our spark plugs, given the added power.

I have a clunk coming from my rear subframe bushings, and so I ordered some powerflex inserts to eliminate that. My suspension guy suggested that the rumble could be coming from the axles, because everytime the rear subframe moves, the angle of the axles changes as it sits in the rear diff, apparently he thinks that could cause some "harmonic" issues.

Has anyone else had this issue? Do you live with it, or what did you do to fix it?
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      11-07-2012, 02:55 PM   #2
cstavaru
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I have that problem, only at low RPMs when going WOT. But really it only seems to be present on Cobb, and I had never heard such noise with GIAC. However Cobb does have more torque at lower RPMs. Not sure what it is, the car drives fine otherwise and I have no lash/play in the diff or halfshafts. I read somewhere that the diff bushings may be soft. Could also be the exhaust.

PS: Why would you not speak the name of that forum member ?
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      11-07-2012, 03:35 PM   #3
KaiserN54
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Quote:
PS: Why would you not speak the name of that forum member ?
I was referencing the forum, not a member.
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      11-07-2012, 05:03 PM   #4
marcvtec
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Not that I believe it is the tune
But since you think it is why not remove it and see what happens
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      11-07-2012, 05:09 PM   #5
JamesM3M5
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It's drivetrain related due to the extra torque. Mine does it, too, sounds weird but is perfectly normal.

Anything you do to stiffen the subframe mounts will transmit more noise to the cabin.
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