Chevrolet 2008 Uplander Owner's Manual page 6

Front Seats
Manual Seats
1-2
Use the lever located on
the front of the seat to
adjust the seat forward or
rearward. Pull up on
the lever to unlock the
seat. Slide the seat
to where you want it and
release the lever.
CAUTION:
{
You can lose control of the vehicle if you try to
adjust a manual driver's seat while the vehicle
is moving. The sudden movement could startle
and confuse you, or make you push a pedal
when you do not want to. Adjust the driver's
seat only when the vehicle is not moving.
To make sure the seat is locked into place, try to move
the seat back and forth with your body.