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SECTION 5
Push Valve Function
Because of the "dynamic brake" feature of the hydro-
static transmission, the tractor can be pushed for only a few
feet before the rear wheels will lock. If the tractor must be
pushed, the manual bypass Push Valve must be opened.
The valve is located on the left side of the tractor above the
footrest.
To operate the valve, follow the instructions on
the "push valve" decal. The valve has a square head and
can be opened or closed with a socket
wrench.
Be sure to
close the valve before operating the tractor. See
Fig.
5-53.
Fig. 5-53 D-Series Push Valve
Hand push tractor only.
Do not tow. Towing can
cause severe damage to the hydrostatic transmission.
Acceleration Valves
Acceleration valves are used in the hydraulic drive circuit
to limit vehicle acceleration to a safe rate.
Two valves are used: a forward valve and a reverse valve.
See Fig. 5-54.
Although the acceleration valves look similar, they are
not alike. The forward valve, located at the rear of
the end cap housing, incorporates wider relief flats on
the valve lands than does the reverse valve, located at
the front of the end cap housing. The forward valve
may be used in place of the reverse valve; however,
under no circumstances should the reverse valve be
substituted for the forward valve.
5-16
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Fig. 5-54 Acceleration Valves
Implement Relief Valve
The implement relief valve is used to regulate hydraulic
lift pressure.
This valve limits pressure to a maximum
of 550 to 700 psi (38 to 50 kg/cm 2 ). The valve is located
to the rear of the pump on the right side. See Fig. 5-55.
The charge pressure relief valve is located on the left, and
limits pump and motor circuit hydraulic pressure to 70 to
150 psi (4.9 to 10.5 kg/cm 2 ).
Fig. 5-55 D-Series Charge and Implement Relief Valves
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