coupling should fit the journal bearing with a relatively close fit. If the coupling has worn through the
bearing and into the aluminum gerotor cover, replace the gerotor cover and drive coupling. If the fit
is excessively loose and the drive coupling has not worn into the gerotor cover, remove the old
journal bearing from the gerotor cover and press a new journal bearing into the cover from the cavity
side. Press the bearing to a depth of 12.88 mm [0.507 in] from the bottom (cavity side) of the gerotor
cover.
Assembly
1. Install the two charge pump cover/pad alignment pins (U025).
2. Install the gerotor cover locating pin (G065).
3. Install the 41 cm3 spacer (not shown) if previously removed. (Spacers exist on the older 41 cm3
models.)
4. Install the drive pin or key (G005) into the drive coupling. Use petroleum jelly to hold it in place.
5. Lubricate and install the gerotor set (G010) onto the drive coupling (U015). Align the notch in the
inner gear with the drive pin or key (G005).
6. If present, install the retaining ring (G006) onto the drive coupling.
7. With the smaller end of the drive coupling (U015) facing up, install the drive coupling and gerotor
onto the shaft.
Different drive couplings are used with different charge pump covers.
8. Place the gerotor cover assembly (G020/G015) over the gerotor assembly and rotate until the cover
engages the orientation pin. The cover fits flat.
9. Lubricate the new gerotor cover O-ring (G023) with petroleum jelly and place it on the gerotor cover
(G020). Early production A pad models may contain two or three seals.
10. Install the charge pump cover gasket, charge pump cover, and auxiliary pump
Charge pump orientation looking inside of gerotor pump cover
Units without integral charge pump
Variable pumps without an integral charge pump have a spacer (G010) in the location where the gerotor
assembly goes. A plug (N004) blocks the charge pump inlet port. Pumps without an integral charge
pump that are not machined to accept a filtration adapter, contain a charge pump defeat plug (R020) in
the gerotor cavity outlet. An O-ring (R020A) holds this plug in place. Later models have an M6 thread in
the exposed end of the plug for easier removal. Replace the O-ring when removing the plug.
Pumps without an integral charge pump that are machined to accept a filtration adapter, do not contain
a charge pump defeat plug. Pumps in this configuration use a full-flow pressure filtration adapter with a
steel O-ring plug (R086) in the charge flow outlet port. The suction filtration adapter does not suit this
configuration; neither does the partial-flow pressure filtration adapter. It bypasses the charge relief valve.
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Minor Repair
520L0638 • Rev 0300 • July 2015 59
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