GR2120 mower deck will not lower all the way. The hydraulics work, the lift link shaft goes up and down, but the adjustment fine tuning bolts attached to the lift link do not bottom out. The deck appears to be held up by the PTO drive shaft. Is this shaft supposed to telescope? If so, it isn't. Could it be the u-joints are not hinging properly? Before I remove the shaft and mess with it, I would like to know if that's the probable problem. Thank you.