Total time on drive was 20 hours.   Steve noticed
the problem as an oil leak from the input shaft oil
seal.  Internal inspection showed the input shaft
thrust bearing roller cage which is a polymer cage
to be partially melted and most of the rollers were
out of the cage.  Overheat was the obvious cause of
cage failure.  Rear race of bearing was seized on
input shaft and was 'blued' from heat. This allowed
the shaft to move back and contact the adapter
plate.  All sorts of nastiness resulted from this
but the details are not as important as the root
cause.  Amazingly, the drive continued to operate
normally but the time between roller cage failure
and discovery of the problem is unknown. The oil passage from the input shaft pilot bearing
to the thrust bearing was found to be clogged and no
oil was getting to the thrust bearing (except for
incidental splash).  What caused the clog has not
been determined.  I will attempt to carefully grind
away the input gear and see what it was as time
permits.   
The rear race was spinning against the adapter plate
and acting as the thrust bearing while being
lubricated only with splash.  That Mobile 1 is
amazing stuff!

A careful inspection of the gears showed no evidence
of damage or wear.

Corrective action:  Replaced the input shaft
assembly and thrust bearing, installed nylon
snubber/spacer to bring input shaft endplay into
spec.

Tracy Crook,   RWS