High,
What could be the cause of a humming sound whose pitch exactly corresponds to the speed of the car?
It starts around 50km/h and appears to come from the front. The transmission is very weak on reverse when cold. Car has over 300 000 km on the clock
Thanks

 

This sounds like a wheel bearing. With your mileage. Jack each front wheel off the floor and grab a hold of the tire at 12 & 6 o'clock, then 9 and 3 o'clock and see if there's any movement.
Wheel bearing noise goes up and down with speed.

 

I have checked the bearings. Couldn't notice any play, rough turning or higher temperature at the hubs. The sound definetely has nothing to do with the revs. It is transmitted to the inside of the car. You don't hear anything through the open window. It has a slight stereophonic quality. You can also feel a very faint vibration through the steering wheel.
Thanks again.

 

Wheel bearing can be broken without any play in it. Jack the car up again ja spin every wheel as fast as you can by hand and listen. Easier to listen/feel when touching the spring while wheel is still spinning. Spring works as speaker.

 

If it is a wheel bearing, the wheel may not turn as easily as it should. In the case of VDP3, the front bearing were very tight and the wheels were a bit hard to turn plus they made a noise. New bearing fix the problem. Weird thing though, I had never had a wheel bearing go bad in any of my pervious jaguars but both were shot on this car at the same time.

 

Silly question, but did this seem to start after you did something like put snow tires on or something? Mine makes a LOT of road noise with my snows on.

 

I think there already was some noise, although not as succinct, before I changed my Michelins to the allyear tyres in fall. I have so far attributed the sound to my tranny as it had the reverse problem and then also to one of my catralytic converters which had a hole. But the sound remained after I had changed the latter. I didn`t worry about my bearings so much because I had changend them around 180 000 km. Both went shortly after each other and had given a grinding sound when cornering, which I don`t have now.
I think I am going to do the spinning check vauxi recommended and maybe get some professional testing before removing the hubs again.