At some point, you may need to remove the mower deck of your John Deere LT155 riding lawnmower. Changing a pulley system, or replacing certain mounting brackets, would be impossible without first removing the deck. Fortunately, the folks at John Deere have made the process of removing the 38-inch mower deck much simpler than it might seem at first. You don't need special tools or advanced knowledge of the LT155 to remove the mower deck.
Remove the spark plug wire to prevent the mower from starting. Put on work gloves. Insert a flat-head screwdriver between the mower belt and the pulley assembly from the top. Pry the screwdriver forward to remove the mower belt.
Locate the lift links on the mower deck. The lift links are a set of nuts with springs to adjust the height of the mower deck. These can be found on each side of the mower deck near the mounting bracket. Adjust the lift links to lower the mower deck by turning the nuts counter clockwise. See "Adjusting Mower Level" in the operating manual for a visual of this.
Support the mower deck with a length of 2-by-4 lumber. Make sure the lumber is long enough to span the width of the mower deck.
Locate the cotter pin in the mounting bracket near each lift link. Grasp the end of the cotter pin with a pair of needle-nose pliers. Bend the cotter pin straight. Grasp the loop end of the cotter pin and pull it free from the mounting hole.
Remove the front and rear adjuster nut. Slide the bold from the mounting bracket. You can identify the adjuster nut by the triangular shaped bolt at the front and rear of the mower deck. The mower deck will slide free from the mounting brackets once these bolts are removed.