Toro Groundsmaster 4500-D Service Manual page 93

Procedure for Rear Traction Circuit Relief Valve (RV)
Pressure Test
NOTE: Adjustable relief valve (RV) in the rear traction
control manifold reduces rear axle motor pressure
created in down hill, dynamic braking conditions to pre-
vent rear wheel lock up.
CAUTION
Prevent personal injury and/or damage to equip-
ment. Read all WARNINGS, CAUTIONS and Pre-
cautions for Hydraulic Testing at the beginning
of this section.
1. Make sure hydraulic oil is at normal operating tem-
perature by operating the machine for approximately ten
(10) minutes. Make sure the hydraulic reservoir is full.
2. Park machine on a level surface with the cutting
decks lowered and off. Make sure engine is off and the
parking brake is engaged.
NOTE: This test uses the same pressure gauge posi-
tion as used to measure traction circuit pressure redu-
cing valve (PR) pressure.
NOTE: The #6 zero leak plug on the inside of rear trac-
tion manifold is a zero leak plug that has a tapered seal-
ing surface on the plug head. Lightly rap the plug head
using a punch and hammer before using an allen
wrench to remove the plug: the impact will allow plug re-
moval with less chance of damage to the socket head of
the plug.
3. Locate rear traction manifold that is attached to the
front frame next to the left side front wheel (Fig. 43). Re-
move #6 zero leak plug on inside of rear traction mani-
fold and install diagnostic fitting (Toro part number
59--7410) into manifold port.
4. Connect a 1000 PSI (70 bar) pressure gauge with hy-
draulic hose attached to installed diagnostic fitting.
5. Start engine and increase engine speed to high idle
speed. Make sure that HI/LOW switch is in the LOW
(mow) position and release the parking brake.
6. Measure and record reverse traction circuit reducing
valve (PR) pressure (see Reverse Traction Circuit Re-
ducing Valve (PR) Pressure Test in this section).
7. Operate the machine in LOW speed (mow) with the
cutting decks lowered. Drive down a slope in a forward
direction, decrease pressure on the traction pedal and
monitor the pressure gauge. Pressure should increase
until the rear traction circuit relief valve (RV) lifts.
Groundsmaster 4500--D/4700--D
GAUGE READING TO BE approximately 550 PSI
(38 bar) and at least 100 PSI (7 bar) higher than
the traction circuit pressure reducing valve (PR)
pressure (e.g. if the pressure reducing valve (PR)
pressure is 450 PSI (31 bar), relief (RV) pressure
should be at least 550 (38 bar) but not much higher).
8. Stop engine and record test results.
NOTE: If the rear traction circuit pressure reducing
valve (PR) pressure is excessive, operation of the rear
traction relief valve (RV) may be affected. Before adjust-
ing rear traction relief valve (RV), make sure that pres-
sure reducing valve (PR) pressure is correct.
9. The rear traction circuit relief valve (RV) is located on
the bottom of the rear traction manifold (Fig. 44). If test
pressure is incorrect, adjust relief valve (RV) (see Adjust
Control Manifold Relief Valves in the Adjustments sec-
tion of this chapter).
10.When testing is completed, disconnect pressure
gauge from the installed diagnostic fitting. Remove
diagnostic fitting from manifold and install removed plug
into manifold. Torque plug to 25 ft- -lb (34 N- -m).
1
FRONT
1. Front frame
4
1. Rear traction manifold
2. #6 zero leak plug
Page 4 - - 53
Figure 43
2. Rear traction manifold
2
3
Figure 44
3. Relief (RV) valve
4. Reducing (PR) valve
Hydraulic System
2
1