from the horse's mouth:

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2010 Defender Puma 90 + BAS remap + Alive IC + Slickshift + Ashcroft ATB rear
2015 Range Rover Sport Supercharged V8 HSE Dynamic



Defender Puma Workshop Manual: https://bit.ly/2zZ1en9
Discovery 4 Workshop Manual: https://bit.ly/2zXrtKO
Range Rover/Sport L320/L322/L494 Workshop Manual: https://bit.ly/2zc58JQ

taken from the ZF 6HP26 Service Information bulletin, but guidelines are probably the same for the 8H version:

Click image to enlarge

Filled for life is nonsense - my LR service document does not mention filled for life but has change gearbox fluid at 10 years or 240,000km whatever is earlier and if used in arduous conditions - such as normal city commuting is to be changed earlier - nothing filled for life - is an urban myth. 07MY RRS TDV6
Arctic Frost
Aspen Interior

it has been known since 1999ish that in Land Rover speak “Sealed for life” means “ Change after 3 years.......” It started in Freelander 1 days when the viscous couplings started to fail prematurely. My local dealership has always warned me when three years has been approaching that it “would be advisable” to change certain fluids 2020 Pangea Green 1st Edition D240 New Defender 110 is here and loving it
2018 Melting Silver Mini Countryman PHEV - soon to be replaced
2015MY Corris Grey SDv6 HSE Dynamic, the best car I have ever owned, totally reliable only a cou0le of rattles in 3 years, now no longer in my care
Also in my garage is a 1996 TDi300 Defender 90 County HT made into a fake CSW

I had the gearbox oil changed in my SDV6 at 70k miles earlier this year. The TDV8 was also changed early at a similar mileage. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

I’m signed up to the Bodsy event on the 19th Jan. Mines on 60k but it’s 12 years old.

Steve. 2006 2.7 TDV6 HSE in Cairns Blue.

You'd be surprised just how dirty the oil is, even at 60k miles...

I recently changed the gearbox oil on my daughters 2013 Ford Fiesta with 48,000 on the clock. Even I was shocked at the condition of the oil which we drained out!

If I ever end up owning a Land Rover which is out of warranty I think that I would be tempted to change the gearbox oil every 3 years or 30,000 miles.

Jim