I had read and my local indy LR specialist agreed that it was a sensible precaution to have the gearbox oil and filter changed on my 120K odd mile 2008 MY 3.6 TV8 not long after I bought it. At the time the car drove fine with no gear change or other issues I was aware of. Following the oil/filter change we started to experience severe TC judder in lower gears accelerating up hills. Took it back and they put an unspecified 'additive' in which cured it. However, now at around 128K miles we are getting an occasional mild judder in lower gears but it doesn't always do it and can quickly be stopped by backing off the throttle and then accelerating again. Moral of the story - I am not sure it was necessarily a good thing to change the oil the first time. Previously a 2008MY Tonga Green Vogue SE 3.6 TDV8

To add my experience on this,I changed the oil on my 07 TDV8 at just under 50k,then did it again 250 miles later. I just got about 4 to 5 litres out each time,so have probably renewed two thirds of the oil. I did not take the sump off either time and it drove fine before,and it drives just the same now. The oil that came out was fairly clean,so maybe a waste of time,but I feel it was worth it. Perhaps best left alone on higher mileages?

I wonder if the answer is different based on whether it's the GM or ZF gearbox? Mine is the soft cheese version, and it seems inadvisable to leave it in there. Seems like an opportunity to at least check the magnet etc with the sump off