Whats that noise???

My Disco2 TD5 has started making a vibrating metallic noise from under the back end...

I thought it was the exhaust banging for ages - it often happens around 40-50, and seems to be as a result of some kind of resonation from somewhere.
It will stop after say 55mph, and if I put the clutch in it makes no difference, so its not engine related - it definately seems road speed related.

I've checked everything underneath for rattles, and nothing seems loose, so I'm a bit stuck now.

The gearbox is quite sticky, but it has done 114k. I checked the rear diff oil and its quite emulsified (yellow).

Any ideas where to look now?

Cheers all

propshaft UJs?

Thanks fer that - how fast were you?

How do I check em then? I did give the prop shaft a good tug up and down, and didn't seem to get too much play. There is some slop in the drive to the wheels, but I thought that was probably play in the diff.
Whats the procedure for checking the UJs

get a screwdriver through the yokes and give it a good tug each way. there should be no play / movement.
for the sake of a fiver each and an hour's work, it's worth replacing them if there's any doubt.

Cool thanks for that Treworgey - I'll have a butchers in the morning!

Change the oil in the axle while you are under there!
You told us it was emulsified.
CharlesY

Righto... I'll try and see if there's anything nasty in the sludge that come out...

Cheers fellas.

Changed the rear axle oil and greased the UJs - no more noises - thanks fellas