Hi Guys,

My 2005 Legacy 2.5 (51,000 miles) has started making a knocking noise.

It only happens when in gear and doesn't happen in neutral or clutch down. (The engine revs fine and sounds normal when in neutral.)
I would say that it is slightly to the left of centre (but difficult to tell when driving).
It gets faster with speed.
It is most noticeable pulling away in second at about 20 mph/2,000 rpm but seems to be there at higher speeds too.
It isn't there on a cold start and only appears once things have warmed up.
It also seems to happen more when steering left, and not as much when steering right.

I was worried about big ends at first, but don't think that this will be the cause if it goes away when in neutral. Then I thought about clutch but can't work out why it would be directional when steering left. So now I think it might be a wheel bearing. What would you guess?

Cheers, Iain.

 

Anyone? Driveshaft maybe?

 

centre diff!

 

Cheers.

Would the centre diff knock when in neutral, or coasting?

 

A worn centre diff will knock when the wheels are being driven and the steering is on full lock (either direction although one direction may be worse than the other). You would feel the knock through the steering wheel though.

The knocking will get faster with speed but shouldn't be noticeable when driving in a straight line. (at least, these were the symptoms when my centre diff went )

If it is only on one side it could be a CV joint.

 

Finally got this looked at. The passenger side calliper was seized and binding onto the disc. The noise only started to happen once warmed up because it took a wee while for the disc to heat up. Should help the mpg now.