Russ, my Patrol had no history when I bought it, but I believe it had been neglected for a long time. I bought it with 210k km on the clock, and seriously doubt whether the wheelbearings had ever been checked before I got it (there were paint alignment dots on the capscrews holding the freewheeling hubs in place). I only paid attention to them when the inner driveshaft oil seals started leaking, at about 260k km. The wheel bearing grease was quite old and dry, but the bearings were still fine.
Furthermore, the Patrol's hubs are very well designed with several "double redundant" seals and HUGE bearings.
I also enquired what the local agents do, and effectively it seems that despite what their own manual sais they only dismantle if they see signs of problems.
I would like to make the following comments:
1) within 2 weeks after any water crossing, it is necessary to check that water has not entered the birfield casings. This is done by unscrewing the bottomost bolt from the king pin bearings and probing with a piece of thin wire.
2) I strongly advise that when the wheelbearings are greased/inspected, the same is done with the Birfields. However then effectively necessitates a diff oil change. I believe that with typical mixed use (say 70% tar) this can safely be done every 100k km, assuming top-quality lubricants are used.
3) I strongly recommend replacing the major oil and grease seals while this is being done, as they are the components with the shortest lifespan. These being the inner axle oil seal (the one in the neck between the axle tube and the birfield), the seal at the inside of the drive flange and the seal behind the large wheel bearing.
4) I buy all the seals from Nissan. I have not found them anywhere else.
5) The bearings used by Nissan are exactly the same (makes, quality etc) as the ones sold by the bearing specialists. So as far as I am concerned, one has to be slightly nutty to buy these things from Nissan at 10 times the price of the exact same thing from Bearings International or Bearing Man? There is one caveat though, and that is the inner (large) wheelbearing, which is slightly modified.
I use Castrol's high-performance greases (lithium for the bearings, Molly for the Birfields). The cost of grease and seals for both sides will be in the region of R2k.
By the way, for some Y61 models, Nissan will not sell the bearings loose, and want to sell you a whole stub axle assembly at R6k each. However, the Y60 and Y61's bearings and most of the seals are exactly the same. There is only one slight difference, in that the Y61 has ABS brakes, which required the omission of one of the backup seals. I don't know about the Y61 pickup though.
Check here for more info including part numbers:
http://patrol4x4.co.za/viewtopic.php?f=45&t=2994
Mag ons ons kenniskry met lekkerkry aanhoukry.