Drive shaft or wheel bearings faulty?

[amebb]

Hi
I have an issue with my car.

When i am driving, lets say 25mph i get a sound from the front drivers side of the car.


It is like mmmmm-----mmmmmm----mmmmm------mmmmmm----mm etc and gets louder as i drive faster.


Now, my car has done about 180k miles and i did noticed that the outer CV boot on the front drive shaft was torn and missing grease.


Yesterday, i replaced the CV boot and applied lots of grease to the drive shaft bearings.


I still am getting the sound. It did get better then worse again after a few miles of driving.


My question is..... without removing the drive shaft and the wheel etc how can i tell if i have a bad front drive shaft or is it the bearings in the wheel knuckle?


If i was to remove the drive shaft from the car and the knuckle how can i tell what is the faulty part here?


Any help would be much appreciated.




Thank you

[andrewwynn]

Three best way I've found to confirm wheel bearing is to swap on a spare tire. If you have 255/55/18 then switch to 265/65/17 it flips which race holds the load and usually makes the sound disappear.

Also, continuous curve one direction should make bearing sound go away. It can be either side for either direction. The sound isn't from vertical loading it's from the wheel being pushed either in or out at the bottom.

255s push out at the bottom, 235s push in.

So for left tires means the forces when going straight are up on outer race, down on inner race. 235 opposite. Curves will flip one side and just increase the force the other side but a right curve can load the right tire onto a bad race it's not always the outside your is why it's difficult to diagnose.

When bad enough, stethoscope the best confirmation.

I thought wife had a bad bearing so i lifted the rear and was about to turn the wheels with car in drive when i noticed cupping on the tires! Was the tires!

"UFO sound" whuh whuh whuh is almost always the bearing. You can use a vibration measuring app to see the frequency at speed and confirm once per revolution it'll be tire or wheel or rotor. 3x or 6x is CV 4.1 or 3.91x wheel speed is drive shaft.

[Masospaghetti]

Wheel bearings often change pitch based on lateral load (i.e. turning). A noisy CV joint wouldn't, although changing the wheel angle "might" change things because it will cause the CV to articulate.


Normally bad CVs make a clicking sound when making sharp turns at low speed, not a moaning sound like you are describing.


To narrow it down further, jack up the vehicle and see if there's any movement/play in the wheel bearing by grabbing the tire and trying to move it. Grab it at the 3 oclock and 9 oclock positions, then the 12 and 6 positions. There should be no movement at all.


Rotate the tire by hand. You might be able to hear the sound and determine where it's coming from.


If you remove the knuckle you can spin the bearing by hand. A good bearing will feel tight and smooth and make virtually no noise. A bad bearing might feel loose, be shedding lubricant, or feel coarse when spun by hand.


I have 2 used OE axles that I pulled from my 2003 as preventative maintenance while I was doing other work. The are definitely used but are quiet and work fine. If you want them for troubleshooting purposes (or need something to get you by for awhile) let me know and we can figure out how to get them to you.

[wpoll]

I've replaced two (rear) bearings on my e53 over the last few years and in both cases, normal methods used for the diagnosis of a bad wheel bearing were pretty much useless.

Because they were rears, turning loads did not affect them much and the sheer mass of the wheel, rotors etc. is so high I could not detect any movement or vibrations when spinning the wheel by hand.

Fronts might be a bit easier to diagnose and the advice offered above seems sound.

In both of my failure cases, one race on the dual-race bearing had bad galling and I was only 100% certain of the fault once the bearing was removed (destroyed in the process - since a slide hammer is the method required!).



And I tell ya - when you pull one of these bad boys, you really WANT to see this exact damage - otherwise you just pulled (and destroyed!) a good bearing!

[80stech]

I used "Chassis ears" and they worked very well for pinning down where the noise was coming from. I've replaced only the right rear brg. once with almost 500k km. I think the right hand is the more common one to give trouble for some reason ??

[wpoll]

Originally Posted by 80stech

I used "Chassis ears" and they worked very well for pinning down where the noise was coming from. I've replaced only the right rear brg. once with almost 500k km. I think the right hand is the more common one to give trouble for some reason ??

I did use a radio mic (Sennheiser EW100) at one point, with the lapel mic taped to the hubs, one at a time!

More load on the right, due to the road camber? Or more puddles'n'potholes on the side of the road.

So in my case, left.

[andrewwynn]

Originally Posted by 80stech

I used "Chassis ears" and they worked very well for pinning down where the noise was coming from. I've replaced only the right rear brg. once with almost 500k km. I think the right hand is the more common one to give trouble for some reason ??

More likely to strike a curb or pothole.

Bearings can last a million miles they don't really wear but comfort l comfier l consider a pot hole might put an impact of 20,30,000# on the 6-7 balls that are holding the weight.

Impact like curb strike is what puts the initial dent that scours away the surface. Enough of a direct relationship that BMW tis calls for replacing any bearing who's wheel was struck in an accident.


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