Chamberlain GS400D Owner's Manual page 16

REMOVE MOTOR ASSEMBLY
4
Remove screws (4) and remove motor assembly. Set motor aside and place in clean, dry location.
NOTE: Turn operator over to remove screws.
DETERMINE MAXIMUM PISTON TRAVEL
5
To ensure proper operation, it is
essential to keep the piston from
extending and retracting completely.
Installation
Screws
"Manually extend piston
out as far as possible and
draw a mark."
"Always stay within these two
marks to prevent the piston from
bottoming out which could
damage the transmission."
16
Motor
"Slowly extend the piston 1/4"
(.64 cm) from collar and draw
another mark."