Managed to get the front and rear diff and transfer case fluids done today. Hasn't stopped the original noise I posted about. So god knows where it's coming from. I found a couple of good sized rocks up inside the splash guards so I wondered if they were causing it, but it appears not.
The fluids didn't look too bad considering they were 110k miles old. Oddly the Ravenoil diff fluid is clear.
The transfer case looked a little dark but no bits in it. So just need to get the gearbox done.
All in, it's a very straight forward job to do. The biggest issue is access to the diff fill plugs. Mr VW saw fit to put bits of subframe in front of them so the only access is with an Allen key. Luckily they are not on too tight. Getting fluid back in could be a PIA. I have a fluid pump that goes in the chuck of a coldless drill, so that with some hose pipe on one end and some air line on the other worked a treat.
The transfer case is easily accessed so no issues there.
I think it's an 8mm Allen wrench you need. I could find torque specs for the diff plugs, but as they required an Allen key I went for just past snug. Basically tighten until it starts to require actual effort.
The transfer case gets done up to 12nm according to what I read, and there should be some high temp sealant applied to the threads to prevent leaks. The plugs are tapered so overtightening will likely lead to bad things!!
I had a look at the prop shaft centre bearing and notes slight play in the bearing so that could be the cause of the droning that I hear. So that will need to be replaced soon. Not sure there are any specialists near me so might just have to be a new prop shaft. Darkside Developments here in the UK do a custom one piece shaft that would be good but it's ~£600.
I have already done the fix for the bearing, the one using the bits of hose pipe. I mean the actual bearing is showing signs of play. If you unbolt the bearing carrier from the chassis and hold the shaft the bearing can wiggle fore and aft. I am assuming it shouldn't have any play in it.
There are a number of aftermarket versions available online for around £300.
And my Treg is no old banger, thank you very much!....... So rude! 🤣