According to the John Deere website, the tractor mower should not be put into reverse unless absolutely necessary. Instead, the mower should be driven forward until positioned at the desired location.
The John Deere tractor will not move in reverse without using the reverse implement switch (RIS). This gear should be utilized only if there is an attachment on the mower or if the mower must be moved in reverse; the tractor will not move in reverse without it. To use the RIS, stop the tractor while it is powered up and look behind you to make sure there is no one or nothing behind you. Push in and hold the RIS on the dash while moving the gear shift lever to “R” for reverse.
If the tractor stops operating and will not move in reverse, push in and turn the RIS back to “Off.” Straighten out the wheels using the steering wheel while the tractor moves. Once the mower is straight and moving forward, repeat the above process to engage the RIS and operate the tractor in reverse gear.
The mower deck may have come off the links that position the deck into place, causing the tractor to be stuck in gear. Park and turn off the tractor, and then wait for the tractor to cool before examining the links that hold the motor deck in place. You can use an adjustable wrench to tighten or loosen the links and move the deck back into position. The sides of the deck should be level and the front of the mower should be approximately a quarter inch lower than the back of the mower.