Gradall 534B (9020-7317) Service Manual - Manual (Page 145)

With the engine running, the converter charging pump draws oil from the transmission sump through the
removable oil suction screen and directs it through the pressure regulating valve and oil filter.
The pressure regulating valve maintains pressure to the transmission control cover for actuating the direc-
tion and speed clutches. This requires a small portion of the total volume of oil used in the system. The
remaining volume of oil is directed through the torque converter circuit to the oil cooler and returns to
the transmission for positive lubrication. This regulator valve consists of a hardened valve spool operating
in a closely fitted bore. The valve spool is spring loaded to hold the valve in a closed position. When a
specific pressure is achieved, the valve spool works against the spring until a port is exposed along the
side of the bore. This sequence of events provides the proper system pressure.
After entering the converter housing the oil is directed through the stator support to the converter blade
cavity and exits in the passage between the turbine shaft and converter support. The oil then flows out of
the converter to the oil cooler. After leaving the cooler, the oil is directed to a lubricating fitting on the
transmission and through a series of tubes and passages lubricates the transmission bearings and clutches.
T h e o i l t h e n g r a v i t y d r a i n s t o t h e t r a n s m i s s i o n s u m p .
The hydraulic torque converter consists basically of three elements and their related parts to multiply engine
torque. The engine power is transmitted from the engine flywheel to the impeller element through the
impeller cover. This element is the pump portion of the hydraulic torque converter and is the primary com-
ponent which starts the oil flowing to the other components which results in torque multiplication. This el-
ement can be compared to a centrifugal pump in that it picks up fluid at its center and discharges at its outer
diameter.
The torque converter turbine is mounted opposite the impeller and is connected to the output shaft of the
torque converter. This element receives fluid at its outer diameter and discharges at its center. Fluid directed
by the impeller out into the particular design of blading in the turbine and reaction member is the means
b y w h i c h t h e h y d r a u l i c t o r q u e c o n v e r t e r m u l t i p l i e s t o r q u e .
The reaction member of the torque converter is located between and at the center or inner diameters of the
impeller and turbine elements. Its function is to take the fluid which is exhausting from the inner portion
of the turbine and change its direction to allow correct entry for recirculation into the impeller element.
The torque converter will multiply engine torque to its designed maximum multiplication ratio when the out-
put shaft is at zero RPM. Therefore, we can say that as the output shaft is decreasing in speed the torque
multiplication is increasing.
The shift control valve assembly consists of a valve body with selector valve spools. A detent ball and spring
in the selector spool provides one position for each speed range. A detent ball and spring in the direction
s p o o l p r o v i d e s t h r e e p o s i t i o n s , o n e e a c h f o r f o r w a r d , n e u t r a l a n d r e v e r s e .
With the engine running and the directional control lever in neutral position, oil pressure from the regulat-
ing valve is blocked at the control valve, and the transmission is in neutral. Movement of the forward and
reverse spool will direct oil, under pressure to either the forward or reverse direction clutch as desired.