Thanks to those who responded to my request for CV joint advice.  The
distance diagnosis winner (again) is Mr. Bulley, who said "Don't worry."
He was right.  Being a sceptic, I cleaned out another joint (being careful
not to let it come apart) and it had the same feel.  Greased them all and
put them back on, cursing the clown who specified socket head bolts with a
torque of 33 lbs.  I still have a whine, so I guess it's rear bearing
packing time.  Groan.