| 摘要 |
A vacuum operated speed range shifting mechanism for use in a drivetrain subassembly having input and output shafts, each being rotatably mounted within a support structure. The shifting mechanism comprises an annular shift sleeve surrounding and splined to the output shaft for rotation therewith, with the sleeve being axially moveable between first and second axial positions corresponding to low and high speed modes of operation of the drivetrain subassembly. The mechanism further includes a stationary annular housing disposed coaxially about the shift sleeve within the support structure. The housing is axially restrained by the support structure and defines an interior chamber. A flexible annular diaphragm is attached to the housing and disposed within the housing so as to divide the interior chamber into first and second annular cavities which are substantially hermetically sealed. A shift collar assembly is attached to the diaphragm and is disposed in surrounding relationship with the shift sleeve. In the preferred embodiment, evacuation of one of the first and second cavities and simultaneous venting of the other cavity to the atmosphere exerts a generally axial force on the shift collar assembly thereby forcing the shift sleeve to be disposed in one of the first and second axial positions to cause shifting to a desired drive mode.
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