Low pitched noise/resonance from drivetrain(?) - any ideas?

[Boston X5 4.4]

Hoping I can get help with a noise that I have noticed for some time. It seems to be worse now that weather is colder.

Its hard to describe but:

- The noise is low pitch/resonance. It is not high pitched/whistle like the noise others have traced to a hole in intake book, hoses etc.

- It is more noticable in lower gears under slow acceleration. It increases with acceleration and gets at its loudest in lower gears just before the auto changes up a gear at about 2,000 rpm. It does not seem to be noticable at higher rpms and higher gears.

- The noise/resonating when it happens seems to be coming from front and underneath.

Any thoughts?

[bds325is]

just had this w my 05 4.4 ...at 87 mph ...which is 2800 rpm...groan in floor....Problem was alternator going bad.. bearings were going bad...caught it before complete failure...Of course to find it I replaced every pulley and belt .

[Boston X5 4.4]

Originally Posted by bds325is

just had this w my 05 4.4 ...at 87 mph ...which is 2800 rpm...groan in floor....Problem was alternator going bad.. bearings were going bad...caught it before complete failure...Of course to find it I replaced every pulley and belt .

Thanks BDS...I thought that the alternator bearings going would be more or of a whining or mechanincal noise.

This is very much a resonance. I think that I can 'feel' it in the wheel well and it seems to be rpm related around ~2,000-2,500 rpm at different speeds.

Thats why I was thinking drivetrain - differential or trans ().

Any other ideas?

[wallyx5]

A wheel bearing can give the same type of sound. One way to pin point if it's a bearing is at the speed or rpm you hear you noise find a curve and load the bear at the same speed or rpm and see if the noise gets louder or more defined. I had a bearing go south recent and I thought maybe it was the transmission going out. But turned out to be the drive side front bearing. Now she is back to driving like new again.

[bds325is]

I truely thought my groan was a bearing or cv joint....never would guess alt bearing...Can you replicate it in the driveway w- just rpm.s?

[1stE53]

I had a Mitsu endeavor do that a few years back. I took it to the dealership on a flatbed!!! Thank God I did because when they took off the driveshaft it fell apart in three pieces!!! It was AWD.

[julezw]

Ressurrecting old thread as I believe I have the same noise the OP described. What was the outcome of the noise on your X Boston?

thanks in advance

[Boston X5 4.4]

Originally Posted by julezw

Ressurrecting old thread as I believe I have the same noise the OP described. What was the outcome of the noise on your X Boston?

thanks in advance

The noise went away so I didn't do any follow up, yep, makes no sense to me either.
One other thing that I remember is that it was worse in colder weather so we'll see in a little bit if it comes back.

....probably worth starting a new thread and asking the techs (Weasel, Killcrap) who are on here to see if they have any ideas.

GL

[julezw]

Thanks Boston,

*BUMP*

No one else have any input on the matter? Things to look for, possible parts going bad that could make this noise?

I'd add my noise is also like a droning noise so I'm fearing something bad like the tranny....but I had rebuilt 45 k kms ago

[tmpE86]

Originally Posted by julezw

Thanks Boston,

*BUMP*

No one else have any input on the matter? Things to look for, possible parts going bad that could make this noise?

I'd add my noise is also like a droning noise so I'm fearing something bad like the tranny....but I had rebuilt 45 k kms ago

Well Bostons noise sounds just like mine.....drives me crazy, just bought this X5 2 months ago and I am ready to get rid of it. I started a thread not to long ago, here's the link

http://www.xoutpost.com/bmw-sav-foru...ew-member.html

I have a squeaking at idle coming from the idler/alternator area....maybe I might try replacing the alternator, never thought it would cause this type of noise.