Hi just been trying to search for this exact same issue, However i do not have a defender im driving a Disco 1 300TDI.
Are many of the parts carryover? and just ratios different?
I have found on here somewhere that the Rear prop "Doughnut" is a factor in the low speed vibration. I had no issues then i raised my disco 2" and now i have 3 issues ha!
I have a grinding when i lift off and kind of match the engines air consumption with the throttle anywhere above 50mph.
A loud vibration at 30mph in 4th gear
and a rumbling from 0mph -20mph?
I suspect the first one maybe bearings however they shouldn't just make noise when i lift off should they? if they were frigged i would expect a constant issue at all turning rates. Would it be the alternative drive angle pulling them in a different direction?
The vibration i think is a loose panel (I suspect the previous owner repaired the front wings with silicone and not actually welded them... (Dont ask please im hurt enough as it is)
And the rumbling may be a Rear Prop Doughnut just being minced by my new drive angle.. V8 Prop has been located and being ordered tomorrow hopefully that cures this rumble. (The v8 disco prop fits direct with rear 4bolt pinion flange right??? please say this is right haha)
This is just a brain dump of my current issues, can anyone direct or confirm my ideas and actions?
Would really appreciate it