New noise

In the last week my 90 has started making loud, graunching noises. It comes from underneath from mid to rear of vehicle. It is fine, (no noise) when under power, but as soon as I decelerate and get into engine braking/ just taking foot off the pedal, the noise comes in. It comes in at around 30mph, in 3rd and 4th gears. Dipping the clutch and going into neutral make no difference.
Ive checked the wheels/discs for stones, muck etc.
Ive had a good tug at the prop shafts....seem ok.
Its sounds like i`m dragging a heavy lead sled when it happens.
Theres no drag on performance, that side is ok.
Any ideas or pointers guys, would be most welcome.

had similar prob - turned out to be buggered transfer box

Check for heavy, lead sled?

Can confirm there is no lead sled Orm

kwhajh....how did it progress? Time scale and other symptoms please.

ok so check transfer box for oil and beyond that condition of oil. I found mine was like "baileys" so kind of knew it was ducked!!!. Having said that, it never stopped working and went through several off roading trips over 3/4 months. Probs is, you never know, it could go at any time if it is transfer box. You can get them cheap but up to £400. Good luck

This turned out to be the rear, rear propshaft u/j seized and getting very hot.
Replaced and is now fine, (and quiet)