Very few if the geraboxes fail because of outright mechanical failures - they are caused by failures brought on by not changing the oil. I cannot remember the ZF recommended oil change times but I think it is about 70,000km where LR have a 250,000km change - why?? Well A long time ago I heard (and I cannot substantiate it) that as part of the EU accreditation process as well as engine emissions other types of pollutants have to be taken into account - and one of these is engine and gearbox/transmission oils so if oil change intervals can be extended then there is less oil to dispose off and this counts towards accreditation for EU.
So who knows but I suspect that if oil changes were done at around 70,000km the number of rebuilds would go down.
When I first started looking at alternative oils a few years back I was not convinced of the sole use of LG6 as there were a number of alternatives around - some people swore they were good and some others started complaining about issues a couple of years later - oil or just issues who knows. Then some of the alternatives were no longer listed as alternatives so I started to become suspicious.
Now I just dont think it is worth the risk. Gearboxes are too expensive and if you shop smart LG6 is not much more expensive than the others anyway.
I think just a drop and fill from the sump and filler plug about every 40,000km is the go - so about 3-4 litre a go and about 1/3 of the volume - all so easy. Also why did they design the sump (even the metal one) so the filter can be changed with out removing the sump.
Anyway my view is to stay with LG6 - on special at Repco of $29 or buy a 20litre drum from ZF for about $25 per litre and do smaller changes more often.
Garry

