I have a '99 S40 1.8 5 speed manual, 76K which has developed a rumbling noise which gradually becomes more of a whining noise at higher speeds. It sounds exactly like a wheel bearing but having jacked the car up and driven the front wheels the bearings are quiet. The mechanic (not a volvo specialist) thinks the noise is in the gearbox but I disagree as the noise is constant (doesn't change pitch when I change gear or coast in neutral).
Any help would be much appreciated.

 

I would look at the tires. You may have one out of round.

 

Thanks tech. All the signs are pointing towards the tyres. I'm taking the car to my local tyre place tomorrow

 

Let us know how it goes.

 

Both rear tyres pentagon shaped on inside edge! Noise now 70% eliminated - suspect will have to change fronts soon too. Any idea what would cause the tyres to get so out of shape on one edge? I've seen this many times on front tyres when the tracking has been out, but not on rear tyres.

 

There is alignment adjustments for the rear as well.

Also it could be the tires. A belt might have broke.