Several days ago daughter was driving her 99 Ranger -- 3.0L V6, 5-
speed, 4WD, 92K miles, serviced regulalry, driven carefully -- when
oil pressure went to zero and check engine light came on.  She shut it
down immediately and had it towed to dealer.

They reported no oil pressure (we knew that) and suggested a new
engine ($800).  I told them to pull the pan and look at the oil and
oil pump and to pull a couple of main bearings look at the mains and
the crank.  They pissed and moaned but did it.

Found:
-- three teeth broken off synchronizer shaft (this would have caused
the oil pump to stop pumping)
-- minor scoring on mains
-- a few metal filings and three broken teeth in the crankcase.

I told them to replace the synchronizer, check the oil pump, install a
magnetic drain plug, and see what happens.  They did, we picked up the
truck Monday and my son drove it all week -- no noise, oil pressure
good, full power, nothing apparently wrong with it.  Changed the oil
today, no sign of metal shavings in the oil.

The dealer gave me the old synchronizer assembly.  The synch shaft
runs through a housing and it looks to me as though the shaft should
turn inside the house -- it doesn't -- shaft is completely frozen in
the housing -- appears that that's why the teeth broke off -- synch
shaft froze, whatever drives the synch shaft kept turning and broke
off the teeth.

Any ideas as to why this thing would sieze up?

Thanks.