| 摘要 |
A tractor transmission is synchronized between four different speeds in each of two different high and low ranges and a reverse range. A top shaft coupled to be driven by the tractor engine has four different gears which are concentrically and rotatably spaced along the length thereof in constant mesh with a different one of a second group of four gears formed on the outer surface of a counter shaft. The counter shaft is selectively coupled to the top shaft by either of two pairs of synchronizers concentrically mounted on the top shaft between different pairs of the first four gears. High and low ranges are respectively provided by a first splined collar capable of coupling the counter shaft directly to a differential drive shaft and a second splined collar capable of coupling the differential drive shaft to the fourth gear disposed about the top shaft via a low range driven gear. Upon loss of hydraulic fluid pressure, a planetary gear arrangement coupled between the top shaft and the tractor engine is automatically returned from a direct drive condition to an underdrive condition by mechanical springs within two different clutches associated therewith. Similar safety features are provided in connection with the front wheel drive portion of the transmission. |
