rumbling grinding noise whilst freewheeling

on my 90 300tdi
whilst under load either accelarating or decelerating against the gear there is no noise and everything seems fine but if the engine runs faster than the gear selected it makes a grinding rumbling noise, also if leaving a slip road from higher speeds and braking the noise is at its worst, also whilst freewheeling at any speeds?
i have been told that it is my transfer box from a so called know it all....
the noise also got worse after fitting my 2" lift?
i hope this discription is clear enough?

check diffs first by feeling for freeplay in diff flange were prop bolts on sounds like pinion bearings

UJ's may be shot on your propshaft, defo worth a check even if it isnt the problem!

I also have this problem on my 300Tdi. I have a few other noises coming from underneath, so will be checking the UJ's at the weekend, hopefully will resolve it. If not, could be the wheel bearings.

noise on overrun is usually diff ,but could be other stuff,crown wheel driving pinion gives a lot of stress on pinion bearings

so would this not be caused by the transfer box?

axle diff ,is usual but in life and vehicles nothing is a 100%,

James is usually spot on with wht he says but.... Mine was the same changed ujs problem solved