Toro Groundsmaster 3280-D Service Manual page 114

Lower Cutting Deck (or Implement) (continued)
Counterbalance
Hydraulic System: Hydraulic Flow Diagrams
When the cutting deck (or implement) is to be lowered, the control valve spool is
moved forward causing the pilot valve to shift open. This shifted valve allows a
return path from the lift cylinders to the reservoir (front axle)
weight of the cutting deck (or implement) causes the cylinders to retract thus
lowering the cutting deck (or implement). As the cylinders retract, the pistons
draw hydraulic fluid from the reservoir (front axle) into the lower portion of the
lift cylinders.
When the control valve lever is released, the lift control spool returns to
the center position and causes the pilot valve to shift. Fluid flow by-passes
passes through the lift valve and on to the reservoir (front axle) and lift cylinder
movement is stopped.
An adjustable counterbalance valve allows cutting unit weight transfer to the
machine to improve traction. On early production machines, the counterbalance
valve is incorporated in the lift control valve. Later production or updated
machines use a different lift valve and a separate counterbalance manifold.
Changes in traction conditions (e.g., moving up an incline) will cause a valve shift
to slightly lift or lower the cutting deck to alter weight transfer. Counterbalance
pressure settings are dependant on the cutting deck used on a machine. Check
the type of counterbalance system used and refer to the Traction Unit Operator's
Manual or the counterbalance kit Installation Instructions for counterbalance
pressure recommendations.
Page 5–30
(Figure 52). The
Groundsmaster ® 3280-D/3320
05138SL Rev B