Lubrication is not an issue as the whole point of their design, is that once the splines lock together, there is no need of lubrication as nothing moves.
It was a good idea but just not big enuff, mine will work on the same principle of almost zero clearances,and a firm push fit, as all the carrier brgs are on the outside of this tube, are very sturdy and have plenty of lube.
The carrier brg nearest the joint on this one has some play in it, it's a quite big taper roller unit
bigger than the other end, the outer cage is 55 mm ID up to 65 mm dia and 12 mm wide.
As this has worn slightly it's allowed the splines to do also with subsequent result, you can see the bright wear on the nose of the present male end where it has rubbed inside the tube.
Both these boxes seem to have been apart before. The main g/box extension has marks on it, traces of liquid gasket and one of the attaching bolts has had ptfe tape added to the threads.
On the transfer box, although the drive train is in many parts, it's all held together by the brgs
and locked in place by a double C finger clamp, it's self secured by a roll pin, through a boss on the spring loaded selector rod.
Some cowboy has been trying to remove the finger clamp without drawing the roll pin.
Fortunately they haven't done any damage and after I pulled it apart I filed the bits up nice and tidy