We have semi retired our old lazer HP. Over the last year i have noticed on one side when the mower is cold it is very jumpy till the mower warms up. Well today my father went out to move the mower and the jumpy side wouldnt hardly move at all and made some nasty graoning sounds. I started the mower back up and let it warm up then it started acting and working fine. Is that a hydro pump or wheel motor? The machine has 2,200+ hours on it and everything is original.