GMC Sonoma 2001 Owner's Manual page 101

When this light comes on, you can shift to the next
higher gear if weather, road and traffic conditions let
you. For the best fuel economy, accelerate slowly and
shift when the light comes on.
While you accelerate, it is normal for the light to go
on and off if you quickly change the position of the
accelerator. Ignore the SHIFT light when you downshift.
Shift Speeds
CAUTION:
If you skip a gear when you downshift, you could
lose control of your vehicle. You could injure
yourself or others. Don't shift down more than
one gear at a time when you downshift.
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If your vehicle has four wheel drive and is equipped
with a manual transmission, disregard the SHIFT light
when the transfer case is in 4LO.
Four Wheel Drive (If Equipped)
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If your vehicle has four wheel drive, you can send
your engine's driving power to all four wheels for extra
traction. To get the most satisfaction out of four
drive, you must be familiar with its operation. Read the
part that follows before using four
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should use two wheel drive (2HI) for most normal
driving conditions.
NOTICE:
Driving in the 4HI or 4LO positions for a long
time on dry or wet pavement could shorten the
life of your vehicle's drivetrain.
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wheel
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wheel drive. You
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