Grinding noise from the rear

[AquaS2]

As per title, after driving up and down the country today, i've realised that once you lift off, you can hear a sort of grinding humm from the rear of the car, i'm not quite sure what it is. Although i have been advised to change the diff seals, could it be to do with that, or could the diff be on its way out?...

Any thoughts fellas?

Cheers

[Acidburn]

check first off if the exhaust rubbers have gone and the exhaust is rubbing on the driveshaft on the drivers side where it goes over the driveshaft, btdt.

[AquaS2]

Will look into that aswel, cheers matey.

[s2driveruk]

check low diff fluid, stone stuck in the brakes, centre propshaft worn (transmits sounds up and down the shaft), totally agree on the sagged exhaust mounts but i suppose could also be any one of the 5 CV joints dry or worn too.

[AquaS2]

Its not the exhaust mounts, had a quick look, sounds like a bearing of some sort. Around town i've never realised it, it's only when u get a chance to lift off the accelerator a tad that you can hear this... How do i go about checking the fluid level of the diff?

Cheers

[Rusty]

Have you checked the echaust clearance on the diff output flange. I had an identical sound to this 18 months ago, it was the exhaust hitting the bolts under acceleration.

[mcandmar]

Had the same problem, you can see the mark on the output flange where it has been rubbing..

[AquaS2]

Time to tackle this again, how can you establish which bearing to change? Or is it a matter of just change one and hope it's the right one, if not try the other?

[S2central.net]

If a wheel bearing is noisy then you should easily be able to feel it moving if you jack the wheel off the ground to give you enough room to feel for movement by gripping the wheel at a quarter to three.

I had exactly the same thing as mcandmar on mine - so much that the dangling pipe made a nice groove in my flange (I need to lie down after typing that). So check your rubbers are good and tight as well.

[AquaS2]

Thanks very much

[s2_wot]

Bearing Identification

You can probably rack up another 5k miles of normal driving from when you hear the bearing beginning to make noise. It'll get prorgessively worse making it easier to identify.

Law of averages with RHD cars is the passenger side'll go 1st. Should be possible to identify without taking off the wheels. Jack it up and spin the wheel by hand. You should be able to rear the rumbling. Put your hand at 3 o'clock and 9 o'clock and pull the wheel towards you (or push it away) whilst turning the wheel from side. You'll be able to feel the bearings rumble.

A bearing that's badly shot won't spin as freely as as a new one. You'll be able to judge the number of rotations if you give it a good spin. Keep an ear out for a sticky caliper while you're doing this. A sticky caliper could be the cause of the bearing failure in the 1st place.

Bearings work hardest on most cars during braking (and simultaneous cornering). If it's safe to do so whilst driving apply the handbrake a little. If this adds to the groan you'll know the problem is on the back axle.

If the rear discs are well worn you could have a brake pad sitting against the lip that is formed around the outer / inner circumferance of the disc.

HTH

Shane

[YELL MAN]

I had the exhaust mount fail on the rear and the exhaust was resting on top of the inner rear cv joint.

I only noticed it when it started making a grinding noise. I fixed the exhaust but the noise has remained.

It looks like the bearing inside the diff has gone as there seems to be up and down play on the flange. I am sure this should not be normal? I have been looking at diagrams of the diff and along with the bearing there seems to be a shim. Will this shim need replacing as well? Is there a kit available?

[BIGGYIN]

Same has happened,to my q90 B2 type 85.
Back box dropped(weak hangers)and rested on the driver's side inner cv joint.(caused oil leak.)
Just changed diff seal and change oil.There is still,a small drone.
I,ll check the wheel bearings,but think it,s the diff bearing?
Anyone got any details on diff bearings(how to check?) and how easy they are to replace?
Thanks,Karl.

[BIGGYIN]

Can anybody help?(Rear diff bearing.)


Has anybody,changed their rear diff bearing(s)?How do you check,the bearings?How big,ajob?
Did it cure,the whine?
Thanks.