Howling noise: Transmission or suspension
 

'97 940 2.3 LPT, manual.

I've started no notice a bit of a howling and vibration felt through the pedals while driving at speeds around 30mph+. Its really intermittent, and steering in either slight direction stops it for a while before it returns. It happens independently of revs, or whether the clutch is disengaged.

My first thoughts were a front wheel bearing, the car's done 250k, but it also occurred to me that maybe its the propshaft bearing, and when I steer, the entire drivetrain is moving a little with out worn bushes. Obviously I don't want to induce any vibrations.

Any thoughts about how to pinpoint the issue? I've tried to get a video of it, but the microphone doesn't pick it up over the road/wind noise.

Just done my prop centre bearing and that was properly buggered at 235k. Manifested as a howling squeaking noise that scale with wheel speed, not engine speed and was there clutch in or out.

You can do it on the drive with axle stands and you don't need a press. Just go carefully with a punch or brass drift and be very careful not to stove the seal of the new bearing in as you shove it down the prop.

Be mindful to mark up the prop at every union and put it back as was including the splines bit that slides back and forth. I used hot pink nail varnish but you don't have to.

If you're brave, you can put it on a ramp and use a listening stick or stethoscope if a mate is willing to give it some Welly in 5th whilst dragging the brakes a bit to induce load.

Another test is to drop the centre bearing and twist it by hand. Definitely don't hold the bearing in your hand if a chum is running the car on the lift though!