DRESSTA TD-25M EXTRA, Service Manual

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SECTION 7C
TRANSMISSION
Page 2
TD-25M EXTRA DRESSTA
GENERAL
2. DESCRIPTION
The transmission is designed to provide gears shifting by using hydraulic actuated clutches. It has
three forward and three reverse speeds. The transmission is bolted to the front of the rear part
main frame, and is coupled to the torque converter by a drive shaft with a universal joint on each
end. The drive shaft rotates the transmission input shaft. The transmission also contains an output
shaft, a counter shaft and a reverse idler shaft.
Directional Clutch Shaft (Input Shaft)
The directional (input) shaft rotates on two tapered roller bearings. The shaft consists of forward
and reverse drive gears, which ride on caged roller bearings and are welded to the dual hydraulic
clutch pack assembly.
Countershaft
The countershaft rotates on two tapered roller bearings. The shaft consists of forward and reverse
driven gears and first speed driver gear. The reverse driven gear is splined to the rear of the shaft
and held in place by retaining rings. It is in constant mesh with the reverse idler gear and the
second speed driven gear. The forward driven gear is splined to the center of the shaft and held in
place by retaining rings. It is in constant mesh with the forward drive gear and the third speed
driven gear. The first speed driver gear is splined to the front of the shaft and held in place by
retaining rings. It is in constant mesh with the first speed driven gear.
Reverse Idler Shaft
The reverse idler shaft is bolted to the transmission cover in a fixed position. The shaft consists
of a reverse idler gear which rides on two tapered roller bearings and is in constant mesh with the
reverse driver gear and the reverse driven gear.
Range Clutch Shaft (Output Shaft)
The range (output) shaft rotates on two tapered roller bearings. The shaft consists of first, second
and third speed driven gears which ride on caged roller bearings. The first speed driven gear is
welded to the single hydraulic clutch pack assembly. The second and third speed driven gears are
welded to the dual hydraulic clutch pack assembly.
Pressure Regulator Valve
The pressure regulator valve (5, Fig. 7C.1) contains three spools. The main spool limits the
pressure at output side of the charge pump to 1790 - 1930 [kPa]. The oil at this pressure is used
for clutch pack engagement. Excess oil from the main spool is channeled to the converter spool,
then to the lubrication spool.
The converter spool limits the pressure in the torque converter inlet to 790 - 930 kPa. Oil leaving
the converter is directed to the oil cooler. From the cooler, the oil is directed back to the lubrication
spool in the pressure regulator valve. This oil and the excess oil dumped by the converter spool is
used to lubricate the transmission. The lube oil pressure is limited to 280 - 450 [kPa]. Excess lube
oil is dumped into the transmission sump. It should be noted that lube pressure will be lower in
gear than it is in neutral.
Range Selector Valve
This valve (10, Fig. 7C.1) consists of one switch spool, one directional selector spools and two
range selector spools which are hydraulically controlled. In "forward", oil pressure is exerted
between the switch spool and directional selector spool, causing the short switch spool to
compress the spring and the long directional selector spool to remain in place.