wsm STW37 Workshop Manual page 201

STW34, STW37, STW40, WSM
Forward Position
When the speed control pedal is stepped on and in
forward, the variable swashplate (11) is tilted as shown
in figure above.
As the pump cylinder block (2) rotates with the input
shaft (10), oil is forced out of pump kidney port A (13) at
high pressure. As pressure oil enters motor kidney port
C (16). the pistons (8), which align with port C (16), are
pushed against the swashplate (9) and slide down the
inclined surface.
Then the output shaft (6) rotates with the motor
cylinder block (7). This drives the machine forward and
the angle of pump swashplate (11) determines the
output shaft speed.
As the motor cylinder block (7) continued to rotate,
oil is forced out of motor kidney port D (15) at low
pressure and returns to the pump.
3-M6
TRANSMISSION
(1) Oil Cooler
(2) Cylinder Block (Pump)
(3) HST Oil Filter (10 µ)
(4) Check and High Pressure
Relief Valve (Forward)
(5) Neutral Valve (Forward)
(6) Output Shaft
(7) Cylinder Block (Motor)
(8) Piston (Motor)
(9) Fixed Swashplate
(10) Input Shaft
(11) Variable Swashplate
(12) Piston (Pump)
(13) Pump Kidney Port A
(14) Pump Kidney Port B
(15) Motor Kidney Port D
(16) Motor Kidney Port C
X: High Pressure Oil
Y: Low Pressure Oil
Z: Suction or Drain Oil
9Y1211109TRM0006US0
KiSC issued 11, 2014 A