Importance

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Abstract

A four wheel drive automatic transmission, comprising: a speed-changing transmission unit; a front wheel transmission mechanism driven by the transmission unit and having a large driving gear and bearings for the large driving gear; a center differential unit having an input member driven by the large driving gear and two output members for driving front wheels and for driving rear wheels, respectively; a transfer with a rear wheel driving transmission having a driving gear member disposed coaxially with the output member for rear wheel driving, a connecting member between the output member for rear wheel driving and the driving gear member and a transfer output gear member driven by the driving gear member; a case in which the front wheel transmission mechanism, the center differential unit and the transfer are disposed; and, an oil separating structure defining separately lubricatable cavities within the case, the structure comprising two seal members, disposed between the connecting member and the case at opposite ends of the rear wheel driving mechanism, whereby the rear wheel driving mechanism is disposed in a cavity within the case which can be filled with a lubricant different from that used for lubricating the transmission unit, the front wheel driving mechanism and the center differential unit, without risk of the different lubricants mixing. The oil separating structure may be so arranged that the cavity for the rear wheel driving mechanism surrounds the other cavity, the connecting member being cylindrical and defining an annular wall separating the cavities between the sealing members.

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First Claim