I had the exact same problem - and even replaced the rear diff. Turned out to be a wheel bearing. In the end I went to my LR dealer, who diagnosed for free and quoted £246 per side fitted. I got a local independent garage to replace both rears for £170 all in.
Its really difficult to diagnose, but there was a scraping noie when the rear wheels were rotated. (only possible with prop disconnected - I too remove dthe VCU to test)
Hope you get it sorted matey
Regards,
Steve