GMC 1997 Safari Owner's Manual page 110

Resuming
a
Set Speed
Suppose you set your cruise control at a desired speed
and then you apply the brake. This,
of course, shuts off
the cruise control. But you don't need to reset it.
Once you're going about
25 mph (40 kmh) or
more, you can move the
cruise control switch
from ON to R/A for
about 1 1/2 seconds.
You'll go right back up to your chosen speed and
stay there.
Remember, if you hold the switch at R/A longer than
1 1/2 seconds, the vehicle will keep going faster until
you release the switch or apply the brake. So unless you
want to go faster, don't hold the switch at R/A.
Increasing Speed While Using Cruise Control
There are two ways to go to a higher speed:
0
Use the accelerator pedal to get to the higher speed.
Press the button at the end of the lever, then release
the button and the accelerator pedal. You'll now
cruise at the higher speed.
0
Move the cruise switch from ON to R/A. Hold it
there until you get up to the speed you want, and
then release the switch. (To increase your speed in
very small amounts, move the switch to R/A for less
than 3/4 of a second. Each time you do this, your
vehicle will go about 1 mph (1.6 km/h) faster.)
Reducing Speed While Using Cruise Control
There are two ways to reduce your speed while using
cruise control:
Press the button at the end of the lever until you
reach the lower speed you want, then release it.
0
To slow down in very small amounts, press the
button for less than 1/2 of a second. Each time you
do this, you'll go 1 mph (1.6 k d h ) slower.