Patent ID: 7404341

Claim:
A transmission system for a tractor, adapted for transmitting power of an engine to axles through a traveling transmission line and also to an externally mounted utility implement through a PTO transmission line, the system comprising: a clutch housing disposed rearwardly of the engine; a main transmission shaft extending from the clutch housing for transmitting power from the engine; a base transmission case disposed and spaced rearwardly of the clutch housing; the clutch housing and the base transmission case being connected together via a housing frame, the base transmission case including an intermediate partitioning wall for partitioning an inner space of the case in a fore and aft direction to create a front space having a front end opening and a rear space having a rear end opening; a differential case connected to the rear end opening of the base transmission case; a receiving portion for the traveling transmission line and a receiving portion for the PTO transmission line provided in the front space, said traveling and PTO transmission lines being disposed parallel with each other; a gear change speed module having a gear change speed case and a gear change speed mechanism for changing speed of the engine power and outputting the speed-changed power wherein the gear change speed case is configured to support the gear change speed mechanism and has a rear end and a gear module input shaft projecting forwardly from the gear change speed case, the gear module input shaft adapted to be operatively connected to the main transmission shaft to receive power from the engine; and an HST module having an HST case and an HST mechanism for changing speed of the engine power wherein the HST case is configured to support the HST mechanism and has a rear end and an HST module input shaft projecting forward from the HST case, the HST module input shaft adapted to be operatively connected to the main transmission shaft to receive the power from the engine; wherein said front end opening is adapted to selectively connect with either the rear end of the gear change speed module or the rear end of the HST module; wherein: when the gear change speed module is selectively used, a PTO power output portion of the gear change speed mechanism is connected end-to-end to the receiving portion for the PTO transmission line and a traveling power output portion of the gear change speed mechanism is connected end-to-end to the receiving portion for the traveling transmission line; and when the HST module is selectively used, a pump shaft of the HST mechanism is connected end-to-end to the receiving portion for the PTO transmission line and a motor shaft of the HST mechanism is connected end-to-end to the receiving portion for the traveling transmission line.