GMC SIERRA 1995 Manual page 20

But don't have a seatback reclined if your vehicle is moving.
A
CAUTION:
Sitting in
a
reclined position when your vehicle is in motion can
be dangerous. Even if you buckle up, your safety belts can't do
their job when you're reclined like this.
The shoulder belt can't do its job because it won't be against
your body. Instead, it will be in front of you. In a crash you
could go into it, receiving neck or other injuries.
The lap belt can't do its job either. In
a crash the belt could go
up over your abdomen. The belt forces would be there, not at
your pelvic bones. This could cause serious internal injuries.
For proper protection when the vehicle is in motion, have the
seatback upright. Then sit well back in the seat and wear your
safety belt properly.
Seatback Latches (Base Level Bench Seat)
The front seatback folds forward to let you access the rear of the cab. Your
seatback will move back and forth freely, unless you come to a sudden stop.
Then it will lock in place.
If you have a Crew Cab, your front seatback is designed not to fold forward.
Access to the rear of the cab is available by using the rear doors.
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