I thought that once you held the lock pedal down and started moving it stayed engaged until you stopped
no, I'm pretty sure when you let off the pedal, it's disengaged
here's what the manual says for my XG3025:
Differential lock pedal
�� When the rear wheel is slipping and the tractor
can not move forward, stop the tractor
temporarily and press the differential lock pedal.
�� Differential lock is effective for working on
slippery ground.
�� If engaged, both rear wheels will rotate at equal
speed. So, It disturbs steering operation and you
cannot turn.
�� Take your foot off the pedal to release the
differential lock. If the traction is equalized, the
lock is released automatically.
�� If the differential lock does not disengaged (i.e.
the turning radius is larger than normal and the
turning is not smooth), depress the clutch pedal
and/or press left/right one-side brake pedal
slightly for a second each other
now in MY opinion, if the tires are slipping and you're not moving forward, you're pretty much already stopped, LOL but I understand that means push the clutch on the gear models and let off the pedal on the hydrostatic drive