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TRANSMISSION CONTROLS
Dana Incorporated TSM-0238 - 6000 Transmission Service Manual
TRANSMISSION CONTROLS
OPERATION OF THE VALVE
The transmission is controlled by the control valve. The control valve is mounted on top of the transmission.
The function of the control valve assembly is to direct oil under pressure to the desired directional and speed clutches.
The control valve has 6 solenoids and 5 shift spools.
1st gear can be selected by activating the 1st solenoid. The 1st solenoid will then allow a pilot pressure of 8,5 bar to move the
1st shift spool. Due to this movement of the shift spool, the 1st clutch is fed with oil under 12.4 bar regulator pressure. The same
priciple is valid for 2nd, 3rd & 4th gear.
There is one 3-position shift spool for FWD, Neutral, or Rev.To ensure that only 1 direction can be selected. The directional shift
spool is held in Neutral by means of springs as a safety feature. You need to apply pressure to select either FWD or REV. When
both FWD & REV are selected the resulting force is 0 and the spool stays in Neutral position.
When the pressure is directed to one of the direction positions, the oil is guided to the modulator before entering the clutch.
The modulator achieves a gradual pressure increase instead of an abrupt increase.
When pressure is applied initially a spool moves and uncovers a vent, which, because if its discharge or bleeding of fl uid pro-
duces a low pressure. At the same time, fl uid fl ows through a restrictor passageway to an accumulator and as the pressure
builds up in the accumilator, it moves the spool back towards its initial position, causing a gradual increase in pressure.
The direction or speed clutch assembly consists of a drum with internal gear teeth and a bore to receive a hydraulically actuated
piston. A piston is inserted into the bore of the drum. The piston is “oil tight” by the use of sealing rings. A friction disc with
internal teeth is inserted into the drum and rests against the piston. Next, a disc with splines at the outer diameter is inserted.
Discs are alternated until the required total is achieved. After inserting the last disc, a series of springs and pins are assembled
in such a manner that these springs rest on theeth of the piston. A heavy backup plate is then inserted and secured by a snap
ring. A hub with ID and OD splines is inserted into the splines of the discs with theeth on the inner diameter and the splined
shaft extending through the clutch support. This hub is retained by a snap ring. The discs and inner shaft are free to increase
in speed or rotated in the opposite direction as long as no pressure is present in the direction or speed clutch.
To engage the clutch, as previously stated, the control valve is placed in the desired position. This allows oil under pressure to
fl ow from the control valve through a tube in the transmission case to a chosen clutch. Once into the drum, oil is directed throu-
gh a drilled hole into the rear side of the piston bore. Pressure of the oil forces the piston and discs over against the heavy
backup-up plate. The discs, with teeth on the outer diameter, clamping against discs with teeth on inner diameter, enables the
clutch drum and drive shaft to be locked together and allow them to turn as a unit.
There are bleed holes in the clutch drums which allow quick escape for oil when the pressure to the piston is released.
The transmission gear train consists of six shafts:
1 - Input shaft
2 - Reverse shaft
3 - Idler shaft
4 - First & third shaft
5 - Second & fourth shaft
6 - Output shaft
A screen mounted in a frame is positioned on the bottom of the transmission case to screen out any foreign material. This screen
is covered by the sump pan. This pan is provided with magnets to catch any metallic particles.
Some transmissions may have an axle declutching unit as optional equipment. This unit consists of a split output shaft with a
sliding splined sleeve to engage or disengage the axle. This is accomplished by manually shifting a lever in the operator com-
partiment, which is mechanically connected to the shift fork on the clutching unit sliding sleeve. This unit, ofcourse, is only used
on four wheel drive machines. On the front drive only or the rear drive only, the output shaft is a one piece type and an output
fl ange assembled only on the required end.
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