I have a John Deere LX178 lawn tractor and the mower deck will not raise/lower. It is all the way down and pushing in the button is how i've ALWAYS adjusted the height. It will not budge

1) NEVER adjust to where the deck wheels touch the ground. The wheels are to ride 1/4" off the ground. 2) The long lever to your left which raises & lowers the deck has 3 settings. 1- Fully back toward you which has the deck raised (called transport mode). 2- Halfway down which is the normal mowing mode (called float mode) 3- Fully away from you which sets the deck fully on the ground. This mode is ONLY used for VERY rough terrain where the deck risks getting pushed into "transport" or "full up" mode & getting stuck there. 3) On front-to-back tilt, the front should be 1/2inch lower than the back for least damage to the grass. Ok-now to adjust "cutting" height. 1) Park on a level, flat surface. 2) Pull the deck lever fully back toward you to put the deck into "transport" mode. 3) twist the "cutting" height knob (just below your seat) to the height you want the grass cut. Has choices by 1/2" increments from 1" to 3.5". The deck in "transport" mode is 4". 4) Lower the deck lever to the midway/"floating" mode point. 5) Adjust each deck wheel with its own peg & pin to have at least 1/4" clearance from ground. Thats it for "cutting height" adjustments
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call your deere dealer,
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Troubleshooting

Service Mower

cant find info for you,call dealer