The John Deere STX38 features a two-blade, 38-inch mower deck. The mower deck protrudes from each side of the tractor. If the mower deck encounters a hard object in the yard, it will knock the mower deck out of adjustment. This can cause a poor cut quality and may cause extra wear to the mower belt. Adjusting the mower deck will take 15 minutes to complete.
Park the lawnmower on a hard, level surface. Set the parking brake and remove the key from the ignition. Check the blades with the mower level tool. Measure the blade tips on each side of the mower deck. Make an adjustment if the blades are out of alignment more than 1/4 inch. There are two adjustment links on each side of the mower directly in front of the rear tires; adjust the lower side.
Loosen the upper nut on the adjustable link. Turn the bottom nut on the adjustment link clockwise one full turn to raise that side of the mower. Check the level; if the deck is still lower than the other side, repeat this step. Once level, tighten the top nut first then the bottom nut on the adjustable link.
Check the mower level front to back. The front of the mower should be 1/4 inch lower then the back for optimal cutting. If the front is lower than 1/4 inch, follow the draft link rods from the front of the mower deck into the frame. On the end of each rod is an adjustable lock nut; turn each lock nut one full turn clockwise with the 13mm wrench. Recheck the level and repeat this step until the front of the mower is 1/4 inch lower than the back of the mower.