I recently replaced the bearings and seals on the differential on the 84 GL
which my son drives.  When I filled the auto transmission with fluid the aft
was being pumped into the differential. In order to find the place where the
fluid was leaking into the differential I filled the transmission, removed
the bottom cover on the differential and placed a mirror so that I could see
the internal components of the differential.  I started the van and waited
for the leak.  The leak came from the pinion oil seal closest to the torque
converter.  From the diagram in Bentley (39.57) the position of the seal is
critical.  The seal can be installed so that it is at the bottom of the bore
and misses the edge of the shaft it is supposed to seal.  When installing
this seal press it in so that it is level with the top of the bore.
Rico Dagastino
Munford, TN