TM 5-3895-346-14
INSTALIATION AND PLUMBING
HYDROSTATIC SYSTEM
INSTALLATION AND PLUMBING
The system in which the hydrostatic pump and motor is operated should provide an environment compatible
with the requirements of the transmission.
The requirements of the complementary components necessary to complete the hydraulic circuitry are
described below.
The arrangement of the components and their respective sizes are shown on Fig. 1, and Plumbing Reference
Chart.
COMPLEMENTARY COMPONENTS
RESERVOIR (FIG. 1, ITEM 1)
A suggested minimum reservoir volume (in gallons) is five-eighths of the total charge pump flow per minute (in
gpm) with a minimum fluid volume equal to one-half charge pump flow. This minimum reservoir volume will
provide for a minimum of 30 seconds fluid dwell at the maximum reservoir return flow in the system.
The outlet port to the charge pump inlet must be positioned above the bottom to take advantage of gravity
separation and prevent any large foreign particles from entering the suction line. A 100 mesh screen is
recommended over the outlet port to further assist large particle separation. The fluid level in the reservoir
must always be above the outlet port.
The reservoir inlet (fluid return) should be positioned in such a way that return flow is directed into the interior of
the reservoir to provide for maximum dwell and most efficient deaeration of the fluid.
A drain in the reservoir is recommended which would permit a complete fluid change without disconnecting
other normal hydraulic connections. This would also provide a water drain and permit flushing in the event of
excess system or component contamination.
A filler port (FIG. 1, ITEM 12) should be provided that minimizes the potential for contamination entering the
system during servicing or during operation. A closed reservoir is recommended to reduce introduction of
contamination and be designed so that the recommended charge pump inlet pressure and case drain pressures
are not exceeded. (Refer to Troubleshooting for Pressure Limits.)
RESERVOIR SHUTOFF VALVE (FIG. 1,
ITEM 2)
It is recommended that a shutoff valve be installed between the reservoir outlet and filter inlet, on those
systems incorporating a filter installed outside the reservoir to facilitate a filter change without a large loss of
fluid and to minimize system contamination.
The minimum inside diameter of the valve should be equal to or greater than the inside diameter of the charge
pump inlet line so that the recommended charge pump inlet pressures are not exceeded. (Refer to
Troubleshooting for Charge Pump Inlet Pressure.)
FILTER (FIG. 1, ITEM 3)
The fluid supplied to the charge pump system must be filtered by a good quality 10 micron nominal rated
suction filter and shall not incorporate a bypass valve. This type of filtration system will give the greatest
degree of reliability in keeping the system free of contamination. Filter clogging causing reduced inlet pressure
to the pump beyond limits specified will eventually result in reduced transmission control response. The
transmission
480
