Thanks cardoc - that is a good link that I will use.
I'd describe the noise as a metallic "clunk" rather than a click. The wheel is turning about 4cm or roughly 1 1/2 inches between clunks. I was just turning it back and forth by this amount (and no further) in the youtube clip.
I am not too sure exactly what I am looking at through the diff drain hole (having never seen an outback diff removed) - I think it is the ring gear, although it is hard for me to tell from the line drawings in the service manual. I think you might have posted the exploded drawing for the rear diff rather than the front diff. I can not find an exploded drawing in the service manual that clearly shows the relative positions of the front diff and the casing (for instance on pages 5AT4 to 13).
I have a suspicion that the carrier bearings are loose, although grossgary describes the noise/movement as normal in the comment below yours. I would be at a complete loss to explain how these could come loose though. It worries me that this amount of movement in the diff is not going to be healthy for the gear teeth in the diff or, for that matter, the rest of the driveline over the longer term. Particularly since I can hear a definite clunk when driving, and I am reasonably confident I have ruled out the other "usual suspects" in the suspension.
When I changed the diff oil there was a small amount of sludge on the magnet, and the oil was just a shade darker than honey colour. Nothing caught my attention as being unusual.
I don’t know a lot about the vehicle’s background. Given the amount of dust and mud I have cleaned, and the places I have found sticks and vegetation, I can assume that the car has been driven over rough dirt roads probably many weekends. The service history was not perfect either, so I knew that I was taking a risk when I bought it.
I’ve had a couple of wins though – changed 4 litres of the transmission fluid and the filter – it shifts much smoother now, and replacing the front CV shafts has eliminated a bunch of noises and made the steering much more positive. The posts on this site have been a valuable reference.
Grossgary, thanks for the tips. Yes, I have replaced the CV shafts (both now) with aftermarket ones, but not long enough ago for them to have failed. I will monitor them closely and if it turns out to have been a mistake I will buy OEMs. I replaced them separately, and on both occasions there was a marked improvement in the handling and noise. The one I just took out was a remanufactured shaft with nothing “obviously” wrong with it, but the steering now feels noticeably more positive and with less vibration.
I am fairly confident I have eliminated the potential sources of the noise you have listed. Struts are good, sway bar and control arm bushings are fine.
The noise is most noticeable when I am coasting (i.e. not using the accelerator) at low/moderate speeds (20-40mph), on a bit of a rough road. I can hear the noise through the floor pan from the front-center of the vehicle and it is definitely not normal road noise. I have a theory that it is being caused by the wheels travelling at slightly different speeds over the bumps and one side going a bit faster, then the other, with the noise being basically caused by what I can hear in the diff when I’ve got the car on stands (see previous post with link to youtube clip).
I haven’t tried your suggestion WRT the rear diff yet – I will take a look tomorrow and see if it has a similar amount of free play.
I take your point about used transmissions – these units should last quite a long time if serviced and treated well. Having said that, I would hope I wouldn’t be replacing this one at 65000 miles
