Main Transmission Oil System. Most main
transmissions are lubricated by a wet sump oil system
which is separate from the engine oil system (Figure
3-3.E). However, the engine oil cooler and transmission
oil cooler may be mounted close together so that they
can use the same blower system to cool the oil. Oil supply
from the transmission sump is circulated under pressure
from a gear--driven pump through internal passages and
a filter to the sump outlet. From this outlet external lines
are routed to an oil cooler with a separate thermal bypass
valve, then to a manifold on the transmission main case.
This manifold is equipped with a relief valve to regulate
system pressure and distribute oil through jets and inter-
nal passages. This lubricates bearings and gears inside
the transmission where the oil drains back to the sump.
3-3.E. Typical Main Transmission Oil System.