??? Vibrations whilst driving

[moranor@axis]

im chasing ghosts in the back of my car...

when i got the car it had a strange vibration in the back...the 2nd hand car dealer changed the left wheel bearing and it went away for a while?

i have not done a 6 speed box conversion with a 3.38 diff (old was 3.07)
this involved swapping boxes, shortening prop and swapping diff

since then the noise is back and now very loud so i cant be sure its the same noise but the symptoms are similar...

at high way speeds it is the loudest when in top gear...if i let off the accelerator and let the engine brake the car it makes a huge noise (sounds a bit like a truck using it air brake)
i can also replicate this in the higher gears when the RPM is about 3000 so i think it is when the engine puts a certain load on the drive chain.
it is coming from the back and there is little vibration in the gear stick so i dont think it is the box...
it is a relitively low frequency vibration so my 1st thought is that it was in or after the diff because it seemed to be relative to the rotation of the wheels...

I have checked the drive shafts CVs and have swapped diffs (seems strange that 2 diffs would make the exact same noise) im taking the prop shaft off on thurs to have another look at it to see if maybe the problem is there...if its not there i will change the rear wheel bearings then have the diff rebuilt

any ideas on what it could be? its driving me insane and im sure the vibration will break something if i leave it too long

 

[Tumo]

Sounds like an unbalanced drive shaft to me. The vibrations seem to be proportional to your rpm and can be caused when there inst even weight distribution on the shaft itself, tolerances on this is minute. This can cause a number of nasty problems including stuffing your diff and gearbox.

Cant say for certain, but that is where I would look first.

Hope you come right!

 

[moranor@axis]

the prop shaft was balanced when they put it in but it was not done right...

 

[Tumo]

the prop shaft was balanced when they put it in but it was not done right...

maybe it is unbalanced again? what do you mean they didn't do it right?

 

[moranor@axis]

the prop shaft was balanced when they put it in but it was not done right...

maybe it is unbalanced again? what do you mean they didn't do it right?

ment to say
"the prop shaft was balanced when they put it in but maybe it was not done right..."

---

after reading this i was convinced it was the diff thats why i did the diff swap but now that they both make the exact same noise im not so sure anymore...

A BMW differential's most common wear item are the output bearings. Output bearing wear is characterized by a hum or whine from the back of the car that will become audible between 3000-4000 rpm, usually more noticealbe in fifth gear at a constant cruising speed. The noise will stop or change when you lift your foot from the accelerator pedal and may also change as the suspension rebounds from dips and valleys in the roadway. The perceptability of the noise is dependent on the load on the bearing The noise may also stop entirely above a given rpm. Also, many cars with differentials showing this wear have gone another 50,000 miles with this noise and no further, so it's not necessarily something that needs to be addressed right away. But the longer you let it go, the more likely it is that other parts, such as the expensive ring and pinion gears, may wear out as well....

 

[moranor@axis]

well it is definately not the diff just had it striped and checked and they guy says its perfect :cursin:
when i 1st heard the noise i thought it was the prop shaft but the mech that fitted it said he was sure it was not...
i will be seriously pissed if it is that now...

 

[Gizmo]

It sounds like your dual-mass flywheel is on its way out, my 330i does the exact same thing, very annoying!

 

[Coisman]

imp:
STOP hiding bodies in your boot!! :nono:
...and if you do, make sure they are indeed dead. :hammerhead:
That way they cant make funny noises that make you think its your car! :thumb:

 

[moranor@axis]

It sounds like your dual-mass flywheel is on its way out, my 330i does the exact same thing, very annoying!

but the sound is defiantly coming from the back?
also cant feel it in the gear knob when the noise comes and goes?
could it still be the fly wheel?

---

imp:
STOP hiding bodies in your boot!! :nono:
...and if you do, make sure they are indeed dead. :hammerhead:
That way they cant make funny noises that make you think its your car! :thumb:

when they get rowdy i hit them with the spade

 

[BMW M]

A bit off topic, but might help,

I had a 1992 Hilux D/cab once that had the same problem after some drivetrain mods for better 4x4 capabilities. Turned out that the shortened Propshaft had a tiny welding hole in the side, was balanced 100%... but at certain rpms would howl like a wolf in heat... used some expanding foam and the problem was solved.

 

[moranor@axis]

the problem is its not always consistent today when i was on my way to work it hardly made a noise but for the last week its felt like the the car is going to shake it self apart...
if it were something like a distorted shaft or a dodgy weld it should not change

the prop is coming off today i hope they find something wrong with it...

 

[moranor@axis]

ok so went to have a look at my car in the workshop...
they found that the rear universal was put together by an R-tard
obviously when they shorted the front of the prop they never bothered to check the back :thinking:
anyway I hope that was the problem

 

[moranor@axis]

:cursin:

well the vibration seems to be gone but there is still a noise...
looks like i should look into a fly wheel?
any other ideas

 

[moranor@axis]

this seems to be similar to what i have...

 

[Iceman007]

usually when the Dualmass Flywheel start showing its on its way or realease bearing. it will start shuddering when you pull away. Ihave learnt that lesson. Complete clutch as from Agents(which is a LUK) from Middas is R5000. But as they said the whine sugests the gearbox.

 

[moranor@axis]

from what i have read when the fly wheel normally vibrates at lower revs...
I have decided to change the rear wheel bearings and see if it makes a difference...
the sound is most definitely from the back and i find it hard to believe that it could be coming past the flex disk and making a noise at the back

 

[Matt Q]

Actually, since you are in an E46 and since you probably drive with a bit of spirit, it may well be your rear mountings... very common problem in all E46's with a bit of age on them, especially if you tend to do the occasional robot race.. the small tears in the sheet metal manifest as squeaks and rattles.. have it checked as a possibility

 

[moranor@axis]

i have had a look because i was worried about sub frame failure but it looks good under there have not checked all the bushes at the back thou...
road surface or bumpiness seems to make no difference to the noise so thats why i think it is drive line related

car was previously owned by a doctor and from what i can see i doubt it was ever driven hard before i got it
I have had the rear diff bush replaced thou and
the diff mount was also replaced by the used car dealer i got the car from it looks fine thou and the bushes on it look good too...but being used car dealers i dont trust what they have put in

what should i look out for when looking at the front diff mount?

 

[moranor@axis]

re checked bushes they all look good
had wheel bearing changed...nothing still the same

If the fly wheel could make a noise from the back then it could also be the gear box
I think i will try change the gear box oil before i start spending more maybe i get lucky
how much oil do the new gearboxes take? im not sure if its from the e90 or the 1 series

 

[moranor@axis]

ok so now that ive lived with this a bit ive realised that 5th gear is completely silent? this makes me think it is a gear box problem...

is there anyway that this could not be a gearbox problem if 5th does not make the noise bout all other gears do?