Overview
Parts may or may not be interchangeable between pre-1998 and post-1998 model year pumps. Many
parts, including the housing assembly, are unique to the model year change.
Description of change
Housing
The port cover for the control spool (FOB option - 28 cm3 only) changed from a flat plate with two screws
to an SAE O-ring boss plug. The screw holes for the servo covers and four of the six screw holes for the
side cover are deeper to accept a 10 mm longer screw. The two holes next to the charge pump cover
stayed the same length.
Charge pump
The gerotor drive pin changed to a parallel key. A retaining ring was added to the charge pump shaft to
locate the gerotor. The outer step on the gerotor cover was eliminated and the locating pin slot depth
increased.
Auxiliary flange shipping cover
The cover changed to a flat cover plate with a special seal ring (not to be used to seal an auxiliary pump)
under the cover (A pad only).
Charge relief valve
The relief valve changed from a non-adjustable to an adjustable relief valve. This change requires a 1998
upgrade housing.
Spool - loop flushing
The spool changed to become common between the 28 and 41/51 cm3 pumps. This change requires a
1998 upgrade housing.
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
1998 Model Release
8 520L0638 • Rev 0300 • July 2015
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