GMC 2007 Sierra 1500 Pickup Owner's Manual page 462

Preset Mode: PTO speed control mode is used
for stationary applications. (PTO will remain
engaged while mobile in the preset mode, however
PTO set and resume speed controls will be
inoperative.) This mode provides a default standby
speed of 800 or 850 rpm (depending on the
engine/transmission combination) and two default
PTO control speeds which follow:
1. PTO Set Speed of 1,250 rpm, or
2. PTO Resume Speed of 1,700 rpm.
Please note that the standby speed (800/850 rpm)
is not to be used as a PTO control speed.
Vehicles not equipped with cruise control will not
have the resume speed capability.
To use PTO speed control in variable mode (while
mobile) do the following:
1. Engage the PTO.
2. Vehicle speed must be greater than 5 mph.
3. Make sure your foot is off the brake pedal
(and off the clutch for vehicles equipped
with a manual transmission).
4. Select the desired engine speed by using the
foot pedal, and select SET on the PTO switch
or the cruise control.
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To use PTO speed control in variable mode (while
stationary) do the following:
1. Engage the PTO.
2. Vehicle speed must be less than 5 mph.
3. Make sure your foot is off the brake pedal
(and off the clutch for vehicles equipped
with a manual transmission).
4. Select the desired engine speed by using the
foot pedal, and select SET on the PTO switch
or the cruise control.
Variable Mode: PTO speed control mode can be
used for both stationary and mobile applications.
This mode allows PTO to be controlled in a fashion
similar to how cruise control sets vehicle speed.
The operator can set to an rpm (between 800 and
2,200) with the cruise control feature or with the
SET position on the PTO switch. The operator
is then able to increase rpm in increments of 100,
or "tap up" with the resume position on the
cruise control. The operator can also decrease
rpm in increments of 100 with the SET switch on
the PTO or the cruise control.
Vehicles not equipped with cruise control will not
have the "tap up" capability.