GMC 2010 T-Series Owner's Manual page 10

Isolator Lock Lever
Lever shown in the Locked
Position
Move the handle down to lock the seat in place. This is
used to reduce backslap experienced while in tractor/
trailer operation or while operating a dump truck.
1-6
The lever is located on
the inboard side of the
driver's seat.
Center Seat
Your vehicle may have a center seat.
To fold the seatback down, pull the lever, located on the
right side of the seat.
Then lower the seatback forward and push down firmly
to lock in position. A storage compartment is located on
the rear of the seatback for use when the seatback is in
the fully lowered position.
Push the lever on the right side of the seat and pull on
the seatback when you are ready to raise it.
WARNING:
If either seatback is not locked, it could move
forward in a sudden stop or crash. That could
cause injury to the person sitting there. Always
push and pull on the seatbacks to be sure they
are locked.