DRESSTA TD-25M EXTRA, Service Manual, Page: 63 / 595

DRIVE TRAIN
SECTION 7
Page 11
DRESSTA TD-25M EXTRA
HYDRAULIC OIL FLOW
6. TORQUE CONVERTER AND LUBRICATION OIL FLOW
(Refer to Fig.’s 7.2 and 7.3)
Pressurized oil from the C port of middle torque converter section pressure regulator valve (15) is
directed by hose to the inlet port of torque converter (6).
After the pressurized oil is used for torque
multiplication, it exits the torque converter at the outlet port and is directed by hose to the inlet port
of oil cooler (7), which is located in one block of radiators.
The cooled oil from the outlet port of oil cooler (7) is regulated by the lubrication spool L in pressure
regulator valve (15) and then directed to the transmission (1) for lubrication purpose.
Cooler outlet oil travels into the transmission clutches for clutches cooling and shafts lubrication.
This oil after cooling and lubrication of transmission collects in the transmission sump. From the
bottom of transmission (1) is then scavenged by hose through an in-line oil strainer (8) and onto
the scavenge element (4) of drive train charge and scavenge pump. From the scavenge pump
element (4) of drive train pump outlet the oil is delivered through hydraulic damper (22) to
the steering drive for internal lubrication purpose by line (20, Fig.’s 7.2 and 7.3). Then oil eventually
drains back into the bottom of the main frame (9).
Leakage of oil from the torque converter (6) is gravity drained by hose from engine flywheel
housing back to the main frame (9). For a more complete description and operation of the torque
converter, refer to SECTION 7B, TORQUE CONVERTER.
7. STEERING SYSTEM OIL FLOW Refer to Fig.’s 7.4 to 7.6)
Pressurized oil M enters the inlet port of steering valve and is available for steering and braking.
The pressurized oil at inlet port of steering valve housing in neutral position of spools allows
pressurized oil from steering valve through the steering valve manifold and onto the drive and
brake clutch packs in steering drive.
This steering drive M oil pressure functions on a range 1790 – 1930 [kPa]. The drive clutch packs
are actuated on a range of 690 – 1930 [kPa] and the brake clutch packs are released on a range
620 – 1930 [kPa]. When the pressure is dissipated below 690 [kPa], the drive clutch packs release
and then the brake clutch packs begin to engage when the pressure is dropping as hitherto.
When the drive train control lever is moved forward (rearward), oil pressure is directed to both
the low range clutch packs and the brake clutch packs. When the low range clutch packs are
engaged, it locks the sun gears of the inner planetary to the stationary steering drive housing.
Power from the pinion shaft, transmitted through the bevel gear and ring gears, turns the planet
gears which are forced to walk around the locked sun gears. This action causes the planet gears to
rotate the planet carrier output shafts and sprocket drives.
When the drive train control lever is in forward (rearward) position and both the high speed range
switches are toggled into HI position, oil pressure is directed to both the high range clutch packs
and the brake clutch packs. When the high range clutch pack is engaged, the low range sun gear
is unlocked, planets are rotating free. Power to the tracks is transmitted from the pinion shaft to the
bevel gear, through the engaged drive clutch packs to the output shafts and on to the sprocket
drives.
When the foot brake is applied, oil pressure to both brake clutch packs is released. As the pressure
drops, springs engage both brakes simultaneously. However, the oil pressure to the drive clutch
packs is not released and the torque converter does the slipping, the foot brake will hold the
machine stationary with the transmission in second or third gear but not in first gear at high idle.
To make a left gradual turn, shift the right speed range switch to its upper (HI) position and shift the
left speed range switch in its lower (LO) position during machine is moving forward or rearward.
The electronic controller will select the left track to low range and the right track to high range.