General
MODEL IIG" HYDRAULIC PUMP
Pwnp Disassembly
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The Model "G" Hydraulic Pwnp is a gear type
pump and develops approximately 900 P.S.I.
It is driven from the belt pulley and is mounted
on the side of the belt pulley assembly.
Oil Circulation
Oi I is drawn through the oil inlet tube which
extends from the pwnp into the reduction gedr
section of clutch housing. Drilled passages
from the tube through the belt pulley housing
connects the inlet tube to the suction side of the·
gears.
Oil leaves the gears under pressure through
drilled passages to the relief valve and control
valve. Oil pas se s th-r-ou.gh the control valve
through the drilled hole in valve which connects
the pwnp pressure passage to rdm.
When the ram is fully extended the pressure
rides high enough (900) to cause the relief valve
ball to leave its seat. At this ti.me the oil passes
the bdll and returns to the swnp through drilled
passage at "B".
When the pwnp bypasses the control lever should
be released immediately. The control lever
spring will then return the control valve to the
hold position. When in the hold position the
valve is turned so the drilled hole does not line
up with oil passages. This traps the oil in ram
dnd holds rams extended. Also the wide notch
in valve lines up with pump passage and oil
passes into wide notch and to lower end of valve
and back to swnp through hole" B". When the
pressure drops the relief valve c1oses~
When the control lever is pushed clear down
the valve is rotated further \D\til both the narrow
and wide notches in valve lines up with the pump
drilled passage. At this time the pwnp continues
to force oil through wide notch and under valve
back to swnp through passage "B". Also at the
same time oil from ranl is released through the
narrow notch and back to swnp.
A sc rew is provided on the pwnp control lever
to regulate rate of drop. Turning screw inslows
rate of drop. The belt pulley and pwnp is of the
clutch type. To shift, depress clutch pedal and
move shift lever towards rear of tractor.
Pwnp Removal
Disconnect the ranl hose or hoses, remove con-
trol linkage, remove capscrews attaching belt
pulley assen.bly to tractor.
Remove the pulley and pinion assembly. The
surfaces of the pwnp body, gedr plate and pulley
housing are lap fits and mated together with
dowel pins. No gaskets are used. Use great
care when separating the se parts to prevent
damage to lapped surface.
The idler pump gear is pressed onto its shaft
and the shaft is mounted in needle bearings. The
pUmp drive gear is keyed to the shaft.
Remove the cover from the control lever. Drive
the taper groove pin from the lever and valve
and remove lever, The valve has an
"0" ring
seal and may be a little difficult but Cdn be
pulled from body.
Remove the pipe plugs from the relief valve bore
and remove relief valve spring, ball seat and
ball. Relief valve seat may 'be driven from body
from spring side. (Enter punch in spring side).
To rt-move pwnp and pulley drive shaft, remove
the detent spring and ball from shift lever.
Remove the bearing cap from housing. Remove
nut on end of shaft and remove the ball bearing.
Move shift collar towards bearing and remove
shift pins. Move the shaft assembly towards cap
side of housing until shaft is out of the roller
bearing on the opposite end. Angle shaft and
bring gears and shaft out through large opening
in the pulley housing.
Press the bevel gear from shaft and idler gear
and thrust washer may be removed.
Remove the taper pin from the shiIter and shiiter
shaft and pull lever and shaft assembly from the
housing.
Inspection
Check the bearings for wear and roughness.
Check gears for wear and roughness. Check the
idler gear thrust washe r for wear. Check the
shifter collar and pins for wear.
Check the pump gears for wear dnd end play.
The gear clearance should be .002" to .004".
Measure the thickness of gear and gear plate to
determine clearance. Gear backlash should not
be excessive. If the relief valve is seating
properly and not leaking the pump should de-
velop approximately 900 lbs. pressure. If it does
not the cause will be found in excessive gear
backlash or end clearance.
G-39
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