If your 4WD has traveled more than 160,000 kms then have the transmission checked for any worn bearing.
If you're not sure what worn bearings sound like then call in and we'll have a listen. Damage can quickly occur when bearings wear, producing minute particles of steel which move around with the oil to interfere with other components.
Replacing the bearings before more expensive repairs are required makes good sense. Remember, prevention is better than a dead truck in the bush or a spoilt holiday
In differentials it's common for the outer pinion bearing to become 'loose' or develop excessive free-play as a result of general wear and tear in the bearings. With thorough servicing it will be detected early and the bearing tension or preload 'can be adjusted correctly' to save further deterioration of the differential bearing surfaces.
Landcruisers, Safari/Patrol and Hiluxes from 1994 to 1997 commonly require attention by now.