F2000 front mower, diesel, 4wd, with HST. Everything works as it should ( blades turn, deck goes up and down, steering moves easily) except for HST. Twice, the unit was working fine and then suddenly stopped. No forward or reverse. Leave overnight and seems to go. I changed fluid (used UDT) and filter. The third time it stopped, it didn't go again. No forward, no reverse. Tried adjusting linkage to compensate for wear (3500 hrs on unit). Didn't help. When foot control is pushed, the engine seems to slow slightly. Drive shaft from engine is rotating.
HELP.
HELP.