Hi there all.

I have been getting a strange burrrring noise over the past 2 weeks in my 968. It has been gradually getting more and more noticable in the cabin.

It gets louder with speed. Is not connected to engine speed or gear. If im moving and put the clutch in it remains.

I jacked the rear of the car up, started the car and put it in 6th. This video is with the other wheel locked and my glamarous assistant taking it to 2000 rpm.

What do you all think? Is it the wheel bearing or am I missing somthing?

Many Thanks

Mark

 

May be the Pinion bearing?

 

I thought that at first

But the noise is proportional with speed. If i'm at 70mph it is just as loud regardless of gear, revs and load. If i put it into neutral the noise remains.

Also with the rear end of the car jacked up it only occurs when the right side wheel is turning. If I lock that wheel and run the car in 6th gear the noise goes away.

So i "think" i can discount the pinion and gearbox from the equation.

I'm just not sure whether this is correct so am looking for info from those in the know.

Mark

 

Sounds like diff gear noise to me. You should get a lot of diff noise if you stop one wheel and let the other spin and this probably is normal. Does the noise disappear if you let both wheel go? Also I would expect to have diff noise the other way around but then the gears rotate differently and it could just be quieter as a result. Also you should be able to pinpoint in your case if the noise comes from the gearbox or the wheel as the car seem to be on stands. If the noise comes from the wheel then is almost likely the bearing that is gone, but it can also be a binding break caliper or perhaps a dead CV.

 

My vote is wheel bearing...

I just did my rear right wheel bearing - it was simply HOWLING - you can let it go pretty far (YMMV) to be sure - mine was confirmed by leakage from the bearing (weaping really).

The bearing change is a non-trivial job - but doable with the right tools.

RK

 

Interested to know more about this. Was it leaking from the front or from the rear of the bearing. Also could you tell with the wheel lifted that there was any play or roughness in the wheel? I am asking as I suspect I have a similar noise coming from the rear (laudest around 50-70 miles) but when I lift the wheels up I cannot see any problems.

 

The weeping was only visable from the rear - there's too much in the way at the "front" (wheel side) to notice anything. But mine was fairly howling by the time I noticed the weep. I didn't check for play or roughness - the weep and the sound were dead give aways.

That bearing is quite large - and deep (twin races) - so I don't know if there would be any play - and they typically fall apart when you pull then out (it's a tight press fit) so I couldn't feel the action once everything was disassembled.

But if the noise is localized - Occam's razor says... : )

You might try taking your rear carpeting out and driving with someone in the back listening to see if it's central (tranny/dif/pinion) or offset (wheelbearing). But that's dangerous - do so at your own risk!

(EDIT) I just watched the video - it actually sounds too high pitched to be a wheel bearing to me - but I never tested my car in this manner - maybe on the road that pitch translates through the cabin to a deeper rumble - or your bearing is failing in a unique way? Maybe try a stethescope to pinpoint the location - but be VERY careful as you to this!

RK



RK

 

I second the stethescope, or disconnect the halfshaft at the transmission and repeat the test. If you still hear it it's the diff. In my experience the bearings don't get play in them, but they do feel like there's sand in them when you spin the wheel with the pads pushed back. This is complicated by the fact you're also turning the trans, though.
Good Luck!
Cheers
Randy

 

That video sure makes a strong case for a wheel bearing to me. That is exactly how I found that I had a bad wheel bearing. My car had the same symptoms and noise and it turned out the wheel bearing was the cause.

 

That's a great data point - I never put my car up - I just heard it while driving - so I guess through the tire/road/body symphony - that high pitch becomes a lower sound.

Makis - let us all know what you find.

RK

 

when i was chasing a noise, i did all of the above to try to isolate(all except access to stethoscope) but could not recreate the noise unless there was weight on the bearing.
mine sounded like a giant mechanical cricket that i would hear bouncing back at me near walls or underpasses, and a low tone growl inside the cabin.
good luck with your search. how many miles on the car? bearings ever been changed? it is more of a typical almost regular maintenance item if you ask me, so more than likely that is your problem.

 

I have put my car up a couple of times and could not hear any unusual noise, even when driving the wheels at speed 60-70mph. The only noise I hear is transmission noise really. I have dismantled the gearbox and could not find anything wrong with it either. I suspect the bearing to be at fault. I have already replaced one bearing from the side I thought I heard the noise but the noise did not go away and now is definitely getting loader. I am reluctant to go replace the other one in case it still does not fix the problem as the job is a pain to do. I am doing some driving tests and I can change the sound of the noise when I turn. When I do right turns the noise seem to diminish a bit. When I go straight or do a left turn the noise seem to be unchanged. The good news is that this test points to faulty rear right bearing which is the one I did not change. But still cannot be certain the bearing is at fault. If I drive with the window down I cannot hear any bearing noise coming from the outside. It seems the noise is transmitted through the chassis into the cabin.

 

the sound changes pitch/loudness when swerving right to left?

wheel bearing.

differential noise will be constant when turning/swerving as the ring and pinion are still turning at the same speed.

 

Hi all,

Thanks for your feedback.

The car has about 106k miles and as far as i can tell is still on the original wheel bearings.

I have not done anything else with this yet. I need to try and diagnose the noise further yet as i'm not 100% sure. I have ordered a stethoscope to help with this but what I am going to do is remove the half shaft as mentioned. At least then i can be 100% if the wheel bearing is involved. On any other car I would just change the bearing but for this I need the Arnnworx tool which i don't have.

There are no signs of any weepage, or none that I noticed.

This noise has come about quite fast, as it wasn't there about 1k miles ago.

I just figure that if I lock the wheel in the video and run the wheel at the other side there is no noise. If it were the diff, would the noise not remain if i did this as the diff would still be turning?

If it is the diff would it be likely to be the 2 outer taper bearings or something more sinister?

Thanks for all your help and hope

Mark