Changed the ARB on my JTD in the last 2 days. Probably took over 7 hours in the end, longer than I thought. However, I wasted a couple of hours having to cut off a rounded nut on the exhaust manifold and also didn't slacken the hidden nut on the transmission tunnel so it wasn't hanging down enough, took a while to realise there was another nut !. Points I'd add to what's been said before are:
1) Exhaust downpipe connection uses stainless ? flanged nuts (12mm) which have little head depth to grip. Stainless is great for corrosion but soft as hell so use a 6 sided socket rather than a multipoint and there's less chance of it rounding. (Maybe JTD specific)
2) There is a 13mm bolt under the heat shield at the very back of the transmission tunnel (near the handbrake cable splitter). You need to remove the heat shield to see it. This bolt needs to be slackened off to allow the tunnel to drop enough at the front.
3) The big centre nut on the rear engine mount is attached to a through bolt and just spins once you loosen it trying to remove it. Don't bother. Just undo the 2 smaller bolts holding the mount to the subframe and the whole lot comes off complete with cast iron bracket bolted to the gearbox. (JTD anyway)
4) You can't drop the subframe enough to get the ARB out without removing the 2 bolts in the wings of the subframe completely. I thought the subframe would move around a lot on the jack with everything disconnected but actually it isn't a problem because it's still connected to the ball joints on the upper wishbone suspension strut things which tend to hold it steady. Once the ARB has been replaced, the subframe pretty much just lifts back up to where it needs to be, just a little jiggling required to align it.
5) I removed the long bolts connecting the suspension strut forks to the lower wishbones (Pubsinger maybe missed this ?)
6) I thought the engine probably needed supporting because it did seem to be putting a lot of weight on the blocks of wood I shoved under it. Also the other engine mounts are towards the front so there seems to be little supporting the rear other than the top torsion strut perhaps. Better safe than sorry especially since you can't avoid crawling around under it.
This job would be really easy on a lift but doing it lying on your back even in a dry garage it's anything but. However it seems I didn't waste my time because the knocking has gone thank gawd
One bush on the old ARB was definitely loose but not massively. The other one was still slightly tight. Can't really understand how it could have made so much noise given the small amount of movement in the bush. I did initially try a spacer wedged in between the bush and collar on the ARB to stop it sliding side to side and it cured the noise completely for about 6 months ... but then it came back with a vengeance. So it must be the bar banging sideways against the bushes that makes the noise. Can't help but think that Alfa could have come up with a better way of supporting the bar that avoided this problem completely. Hell of a waste chucking away a perfectly decent ARB just because of a worn bit of rubber.
Oh and I used one of these 12V impact wrench things to get the steering rack bolts off. Cost about 30 quid and worked like a dream. Limited use only though, it's a bit plasticky !