HI LandySi - did you get this sorted out yet? You are not alone! Went through all the steps - props off, checking oil - changing the prop etc. I still have whining and resonance in my Defender 90 with a 2 inch lift. I changed the transfer box and gearbox anyway, so that has ruled that cause out. The flange at the old transfer front had started to seep though.
I have put in a Disco double carden front prop - a little stretched so I will get a spacer in there. Still getting whining and a little knocking in there - you can actually hear the props whirring away at speed - and the lift seems to contrbute to the whole vehicle magnifying the sound like an echo chamber!
Some guys say double carden, others say wide yolk. I am wondering if I should now try the latter? A custom one is 130 quid from the Prop Clinic. Maybe I need one front and one back?
I do remember Lightweights had this proplem and often wore out diff flanges in no time.
So - is it wide yolk or double carden guys? Is it one prop or both? Any advice welcome.
Thanks