... and for once it's not because of the repair bills :-)

For quite a while now I've had a groaning noise under moderate load. It is just audible over all the other noise at about 40mph but becomes quite noticeable above 50mph, and is only present when I'm just on the throttle - not accelerating, not on a trailing throttle, but just "pressing on it" slightly. It's road speed related rather than engine speed related, and sounds almost like a wheel bearing except everyone else I've asked agrees that the bearing seems fine with no roughness or movement. Oh, going round corners doesn't affect the sound. Mild bumps do, a bit.

I did wonder if it was the nose bearing in the diff, but I'd expect if that was bad there would be enough movement to make the seal leak.

One other clue is that I can feel the vibration through the driver's footwell floor. I've almost convinced myself there's an errant socket stuck on top of the gearbox pressing into the transmission tunnel, or some damn thing :-D

How safe is it to drop off one or other propshaft and take the Rangie up to a decent speed? I'm concerned that might eat the viscous coupling in short order. Any other suggestions for how to pin down the noise would be welcome. I'll post an audio clip just as soon as I can work out how to get it off my phone.

CV joint on the front drive shaft? That's what I'd say if it was a jeep....

I've been told that wheelbearings not necessarily have to show play when worn, as for a grumble at the speed of wheelrotation I'm in the same boat.

Thing is it doesn't really sound like any bad wheelbearing I've heard. Normally there's a kind of "cyclic" noise but this is a steady drone.

Also, I'm not sure a wheelbearing would make the floor vibrate.

I had a groaning that seemed to peak at around 65 mph and that was the nose bearing on the rear diff.

Dropping a prop off won't do any harm in the short term and will tell you which end it's coming from. Or you could do what I did and gaffer tape a mic to a diff, run the cable into the car and record the noise it made. Even a good one makes an evil noise when you go from on load to off.

I'm coming back round to either propshaft or bearing. Here's a recording of the noise, although it's nowhere near as pronounced as it is in real life and it sounds like the diff is howling! At the latter part of the recording I'm doing 60mph and you can hear the noise come and go.

I stuck that into an audio editor and did a little FFT on it, and there are big fat peaks at around 36Hz (2200rpm/60, so engine speed) and a bunch of harmonics, and 42Hz and a bunch of harmonics. Now the tyres are standard 235/70R16s, so they do about 700rpm at 60mph, multiplied by the 3.54:1 diff ratio and you get 2478rpm, divide by 60 and you get 41-and-a-bit revs per second.

Science. Solid Science. Honest guv.

Hmmmm ! That's a hard one to pin point, I've done all 3 on mine ( prop,wheel bearings and diff change ) only way to eliminate the prop is remove and go for a spin, but I'm more towards diff noise, my prop was clicking more than humming, but it's one of those dilemmas, when changing the diff, do you replace the wheel bearings ? Sometimes cheaper to grab a good second hand axle complete..

It certainly sounds very similar to when my diff nose bearing was shot. There was no play while trying to waggle it about but once it was out, turning the input shaft and it felt decidedly notchy.

Finally got a chance to take the props off, and found something rather odd. I decided not to do the rear UJs despite having new ones right there, and I'm rather glad I did...

When I took the front prop off, one of the bearings looked like this. It doesn't look that clear in the pic, but there was a round witness mark on the bearing cup that matched the edges of the circlip - like the cup had been spinning round and round in there. Also there was that powdery brick-red dusty rusty crud that you get when things have been really hot. That was on the transfer case end, too.

So I changed that, and of course lost the phasing of the propshaft because the mark I made wasn't nearly clear enough. There seems to be some debate about whether P38 props are straight or phased, and having the "short" end two splines in front of the axle end seems to cause the biggest fights on other forums, so I figured I'd try it.

Now I've got a tiny bit of groaning noise as before (much quieter) with the suspension on normal height, that goes away at 60mph+ on motorway height, and none of the weird shunting vibration I had before on smooth tarmac that felt like I was running on dumper tyres.

I had a similar experience, noise from somewhere that was much less at motorway height. I figured that slop in the splines would be worse when the prop was extended so bought a new front propshaft. That one was a Bearmach OEM but when I came to fit it, I noticed that the UJ's were in phase. The original that I took off had a spline missing so it could only go together out of phase but the new one didn't so could go together anyhow. I pulled it apart and fitted the two halves together with it out of phase by the same amount as the original. No noise at any height.

Just for the record, how much out of phase they have to be?
If memory serves me right the Classic had to be fit some 90º out of phase.