Insane noise from rear end - diff or bearing?

[PranK]

I'm trying to prep the dirty 30 (330i) for sale.

One issue I have is that the car becomes deafening at around 60 - 70kph. The noise is definitely wheel speed related rather than revs. It sounds like loud-tyre noise but amplified 10 times. There doesn't seem to be grinding or metal-on-metal etc.

I've done the diff fluid on this car about 12 months ago. I believe the noise was occuring then also. Made no difference.

I'm leaning toward bad bearing (passenger side done last year) but I've never heard of them being *this* loud. You honestly can't have a conversation.

Any ideas?

Thanks guys.

 

[r32-25t]

@Dose Pipe Sutututu 

[Dose Pipe Sutututu]

Wheel bearing, this happened on my shit box R33 as well.

[Duncan]

wheel bearing is normally a whoomp whoomp noise like a falcon taxi. If it is bad enough to be a grinding noise you might be able to confirm by jacking wheel off ground and trying to wobble it side to side.

also, generally the outside bearing is noisy in turns so that might help narrow down the side

[PranK]

Love your work guys thanks.

@Duncani was going to wiggle the wheel that was my next test.

[Kinkstaah]

Diff or rear wheel bearings. It kinda has to be. (though it could be a tailshaft... what else rotates back there?).

The comically loud diff whine I have had in the past was due to the crown/pinion gear being f**ked. Messed up bearings is generally a low grinding/rumbling sound.

Diff is usually a much higher pitched whining...right?

I've had a wheel wobble so badly it almost fell off, and I wouldn't say it was ever loud enough to be conversation-stopping, whereas diff whine was alarmingly loud, piercing but the car "drove fine".

[The Bogan]

I would say bearings, my worn couplings and centre bearings on the tailshaft had high speed vibrations, but no actual "noise".

[MBS206]

Wheel bearings.

I've had two cars do it like that.

One was a Honda Jazz. Horrible just loud deep noise, exactly as you describe, sounds like road noise but 10 to 20 times louder.

 

Second was our Subaru Liberty GTB.

Exact same thing. The part that made this one harder to diagnose. The wheel wobble didn't exist. "Sealed" bearings that dried out, and got silly loud.

 

Way to identify, is have someone stand on road side, drive past at about 60.

Turn around, go back the other way. Side that's louder is your bearing issue.

 

Diffs typically have a higher pitch noise than the sound of road noise.

 

So far had 3 wheel bearings go on 3 different cars, only one went whomp whomp whomp like Duncan said. Funny part, it was a Ford Falcon that did it! Bahahaha

[GTSBoy]

Good one @PranK. A year later and no update on the cause of the noise.

[PranK]

  On 08/03/2024 at 5:23 AM, GTSBoy said:

Good one @PranK. A year later and no update on the cause of the noise.

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Woops, forgot to update.

Yep, was the bearing. And, still havent sold the car! 

 

Thanks all for the replies! SAU crew to the rescue once again!