I have a 2005, 2.7 RRS with 75k glorious miles travelled under her. ('Her' as it's so bloody temperamental). Over the last few months I've noticed an increase in a whining, bearing rumbling type noise. Originally I thought it might be a wheel bearing but after a bit more research I think it may be diff related.

Observations -
Noise most noticeable over 50mph
Noise hardly there on acceleration or steady power, but kicks in on release of the accelerator (over-run)
If I change into Neutral noise pretty much disappears until I select Drive again
No change in change of steering direction

Conclusion -
From what I've read this could be the rear diff pinion shaft bearing?

I'm no mechanic but do have access to a workshop with a lift at work. Can anyone confirm likely fault from this scrap of information, and also is it viable to replace the bearing (if that is the problem) or is it a new diff required? In addition, I'm thinking of renewing all the oils in both the diffs and the transfer box. Is this a good idea or a waste of money?

Any advice greatly appreciated.

Also, any thoughts on renewing the gearbox oil, though I understand this is not easy so maybe should leave alone for now. I don't have any gearbox problems currently but want to keep the car running for at least another 5 years

change the gearbox oil and filter if you want to keep the car for another 5 years. but indeed that is a tidious job as the access is very limited.

removing the diff is OK, then you can have it inspected by a specialist who can replace bearings, reshim etc.

OK so now I'm confused......Spoke to two different Land Rover Specialist Garages and described the same fault. One said 'sounds like the prop bearing, had to change loads, hardly ever had a problem with the Diff), then spoke to another who said 'almost certainly the diff......done loads recently, about £400 to rebuild). Anyone got any ideas of how to definitively work out which is at fault?

So, took the car for a drive with an experienced mechanic in the passenger seat. He was '95%' certain that the noise was coming from the nearside front bearing. I was pleased with that diagnosis as it cost less to replace the bearing than have the diff repaired, and others have spent money on diffs to find it was actually the bearing. I replaced the bearing (hub assembly), but alas, rumbling still there

Update: Took my car to IAWA 4x4 in Wellingborough, as from a telephone conversation they appeared to know what they were talking about. Left them the car at 08.30, picked back up at 15.30 and the problem was solved. Front Diff was removed, re-conditioned with new bearings etc and re-fitted, total cost £430. Big thanks to these guys for their professionalism and reasonable charges.

It's nice to hear some good news

Glad you got it sorted tony

The chap who runs IAWA4x4 is a member of the Northants 4x4 forum and well regarded thereabouts. I used him to do a gearbox fluid and filter change a couple of years ago based on recommendations. Found him to be as described. Oh, and there's an American-style diner on the industrial estate that serves a reasonable breakfast!  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Good recomendation here. I'll keep note! I'm not Fat. RRS TDV6 HST.