just a note to M series owners who might have hydraulic shuttle issues. might save you some frustration. over time, the shifter cable might need adjustment on the steering column due to stretch if there is clutch (wet) engagement problems in either direction. this is done via turnbuckle adjustment on the steering column. a half turn in either direction should correct that problem, an easy fix. however in my case, the shuttle engagement problem still existed. the problem turned out to be the cable itself was not fully allowing engagement (restriction, sticking). to replace the cable requires dropping fuel tank & feeding it through the deck. mine is open station, a cab may be different.... not an easy job, but upon cable replacement, the hyd shuttle works like new. thankfully, nothing internal in the transmission. just a tip for those who might experience same problem. wish there was a way of cleaning/lube the cable, but hopefully it will not happen often. best regards