[dg_hans]

Hi y'all,

Unfortunately, I'm having to make my first post here. I bought a '12 E91 xdrive a few weeks ago with 71k miles and brand new Continentals. The day after I bought it, I noticed a pulsating, deep bass-like sound at 50 MPH coming from the rear. The noise only happens between 45-60MPH and then dissipates. There *may* be a slight vibration around 70+ MPH but I'm new to the car and BMWs, so I'm not sure what is normal and what isn't. The noise also seems to get quieter after a few hours of driving but is still present. All in all, I've put 2k miles on the car since noticing the noise (on various roads/highways) and it's not getting better or worse.

I changed the fluids in both diffs and the TC hoping that would solve the issue and it didn't. I then had the tires rebalanced, no change. The noise doesn't change with varying RPMs, different gears, or turning. It's just between 45-60MPH. I took it to my mechanics, who originally thought it was the tires. They swapped my tires and rims with another BMW they had, also with new tires, to see if that solved the issue - no change. They said it might be the driveshaft but they aren't 100% sure and don't want to throw parts at it for my wallet's sake. They also didn't see anything wrong underneath the car. No error codes either.

Does anyone have any ideas as to what it might be? I'm pretty sure it's not a wheel bearing. Based on my research, it seems to be something with the driveshaft, maybe the driveshaft flex joint or center support? I'll be able to get my car on my friend's lift in a few weeks but wanted to see if anyone had any additional ideas for what to check when I get it in the air.

Thanks in advance!

[e90lorkp]

Hey did you ever figure this out? I have this problem too. 2011 335xi. I've seen posts where others describe the car resonating in a similar speed window:
https://www.e90post.com/forums/showthread.php?t=1185287
https://www.e90post.com/forums/showt...ight=resonance

It's loudest around 55 mph for me (GPS speed, not the artificially high speedo reading) and according to a neat phone app I have the vibration's frequency at that speed is the same frequency of the drive shaft.

[eljay]

It's likely the Driveshaft Center Support Bearing (CSB)

https://www.pelicanparts.com/BMW/tec..._Replacing.htm

[dg_hans]

e90lorkp Hey I did. It was the rear driveshaft. I'm not sure if it was the driveshaft itself, the guibos, or the CSB. The driveshaft seemed to have spit out some grease (which it shouldn't have given it's sealed), the guibos had a few hairline cracks, and the CSB had a little play. I replaced them all.

As for purchasing the parts, Driveshaft Specialists of Texas was recommended to me, but the first driveshaft I received was unbalanced and the second had the correct ends welded on the wrong side. Unfortunately, I can't recommend them after that experience. The Febi driveshaft (OEM) did the trick. All noises and vibrations stopped after it was replaced.

Hope this helps!

[e90lorkp]

Thanks for your response dg_hans. I've since identified that my drive shaft is bad too. It was only once I took the drive shaft out of the car where I could see how notchy the rear joint is (I have the style that has a CV join in the rear and screws onto the differential.

In my search for a replacement driveshaft I haven't come across a Febi unit. I've just seen Dorman, which I understand is a relabeled Powertrain Industries. What site did you get the Febi unit from?

[dg_hans]

Originally Posted by e90lorkp

Thanks for your response dg_hans. I've since identified that my drive shaft is bad too. It was only once I took the drive shaft out of the car where I could see how notchy the rear joint is (I have the style that has a CV join in the rear and screws onto the differential.

In my search for a replacement driveshaft I haven't come across a Febi unit. I've just seen Dorman, which I understand is a relabeled Powertrain Industries. What site did you get the Febi unit from?

e90lorkp Sorry for the delay. My mechanic was able to source it from Febi. I get my car worked on at Atlas Motors. They might be able to help you 919 831-2424