Applying sufficient main pressure to the top of the valve moves down
and allows main pressure to flow through. If the pressure exerted by
the spring exceeds the main pressure, the valve moves up, stopping
Directing brake apply pressure to the bottom of the valve requires a
higher pressure to push the valve down; therefore, the same amount of
pressure flows through the valve during braking operations.
valve also contains an orifice for metering and maintaining clutch
x. Clutch Trimmers (fig. 1-39).
The clutch trimmers consist of
an orifice trimmer, plug, spring, and stop. Applying clutch pressure
to the trimmer valve moves the valve and the plug down together until
the trimmer uncovers the exhaust port.
The pressure continues to
flow through the orifice in the valve, pushing the plug down on the
When pressure on the bottom exceeds the pressure on the top, the
valve pushes back up covering the exhaust orifice and stopping the
This procedure only takes about one second in
actual operation and avoids shift shock by softening clutch