300 tdi drivetrain issue / noise

I recently picked up a replacement 90 300tdi, 99 plater, (that had fairly extensive service history), and drove it some 250 miles home. I'd checked the usual levels in the engine bay but not axles, gearbox / transfer etc- a mistake maybe but you hope with loads of paperwork that all this has been dealt with...got it back to Kent but there was what can only be described as a light metallic scraping kind of noise coming into the cockpit that appeared to be coming from the front somewhere, but it still pulled ok, then the noise stopped. A day later after a short trip locally, there was vibration, juddering from the drivetrain (sounds like front) to the degree that I had to stop, before it came to a halt by itself. I've now checked the axles, and rear level was fine but oil looked ropey, so replaced, front a little low so topped up. About to check the 'box levels, but failing that - all wheels move freely when jacked up, so it's not a wheel bearing, either. Can anyone shed any light on what this may be, the only audible noise it makes now is a bit of squeal when in motion, take it out of gear and freewheel, and no squeal?

Take the front prop off and see what difference that makes...

nd while your taking the prop off, check the UJ's on both front and rear props, and see if there is evidence of a missing balance weight too.....

A bit drastic I know, but (if you can) check bell housing for oil and then the crankshaft seal behind the fly wheel.

My 300tdi engine had a whining noise which just appeared one day so I've just replaced it (for another reason) and when I pulled it out the bell housing was full of oil and the seal had clearly gone!

Sounds like a UJ. Very difficult to locate which one - it could easily be the one at the back of the rear prop, even though it doesn't sound like it. They need to unloaded/free moving to check for wear sometimes.