An automatic transmission has many seals and gaskets to control the flow of hydraulic fluid and to keep it
from leaking out. There are two main external seals: the front seal and the
rear seal. The front seal seals the point where the torque converter mounts
to the transmission case. This seal allows fluid to freely move from the converter
to the transmission but keeps the fluid from leaking out. The rear seal
keeps fluid from leaking past the output shaft.
A seal is
usually made of rubber (similar to the rubber in a windshield wiper blade) and
is used to keep oil from leaking past a moving part such as a spinning shaft. In
some cases, the rubber is assisted by a spring that holds the rubber in close
contact with the spinning shaft.
A gasket is a type of seal
used to seal two stationary parts that are fastened together. Some common gasket
materials are: paper, cork, rubber, silicone and soft metal.
Aside from the main seals, there are also a number of other seals and gaskets that vary from transmission
to transmission. A common example is the rubber O-ring that seals the shaft for
the shift control lever. This is the shaft that you move when you manipulate
the gear shifter. Another example that is common to most transmissions
is the oil pan gasket. In fact, seals are required anywhere that a device needs to pass through the transmission case with each one
being a potential source for leaks.
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