Diff ? Prop ? Or other advice needed

Happy new year to all, Been out in my 300tdi disco today, and there is a noise sounds like the diff whining ? when you put your foot down the noise comes on, throttle off & it goes away ?, also seems hard to get it to go over 70mph, at times it feels like its only running on 3 pots & the viabration comes through the body, the disco is a manual, starts & ticks over excellent, revs excellent when sitting still, this has got to be something simple, any ideas before I start looking for the problem, thanks.

Any noise on throttle I trace starting with the rear prop donut, then the UJ's, the front prop UJ's, then diff and transfer box outputs. If they're all fine I'd then look to getting it running with all four wheels off the ground up to speed enough to trace the noise source .. so many things it could be .....

The lack of power could be a turbo problem, a fuelling problem (veg oil goes thick when cold, for instance), the whine might be a lunched fuel pump, a lubrication problem, there's a whole world of possibilities.

Dunno why you think it _has_ to be something simple, it's also a possibility that the gearbox/transfer box/clutch/crankshaft is completely lunched ...

Do what PAULD says, sounds very similar to symptoms with elmer last year, one UJ on the prop shaft was totally mashed, not difficult to find, get under neath and twist the prop shafts and watch for movement in the joints.
Manual says use a long bar to take up play and check for slack, I didn't need one it was so far gone I got aboout 10 degrees of play by hand.
This won't affect speed though, so that may be something else as well

Well I have been away fishing tonight & got under the disco to see if I could find anything, The rear donut is donald ducked ! so I guess that that is the start of the repair process, maybe just that ! as it was running excelent & quite 2 days ago with no noises .

You caught it Ok then . once they 'go' they don't last long at all .... Nice one ...

Paul D said:

You caught it Ok then . once they 'go' they don't last long at all .... Nice one ...

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Just in time I think, just hope all is well when I replace it tomorrow & thanks for you input.

Still worth checking the UJ's as well .. once anything goes on a prop other stuff often follows due, I think, to the extra vibration of the first component going .. )

Well all fixed, it was the rear donut, that connects the prop to the rear diff ! £22.40 for the part & 20 minutes later, fixed, spot on, no viabrations, no problems at all.