threads on the rear bearing cover assembly. Leakage will result if this sealant
fails.
3.
Check the rear bearing cover gasket and nylon collar. Verify that the collar and
gasket are installed at the chamfered hole that is aligned near the mechanical
speedometer opening. The fastener must be torqued to specification with thread
sealant applied to the fastener thread. Use the same procedure to check an
electronic tailshaft speed sensor.
4.
Check the output yoke retaining nut for tightness. The retaining nut should be
torqued to specification (typically 450 to 600 ft.-lb.). You will need a yoke holder
to hold the yoke stationary. A torque wrench capable of handling 600 ft.-lb. or a
lower-rated torque wrench used with a 4 x 4 torque multiplier is required to
accurately torque the nut.
CAUTION
Overtorquing a transmission output yoke retaining nut can cause output shaft bearing
failure. Using a 1-inch air gun to tighten yoke retaining nuts should be avoided, although
it is okay to remove the nut using this tool.
5.
Check the PTO manifolds and gaskets, making sure the fasteners are torqued to
specification.
CAUTION
Many fasteners used to couple flanges and manifolds to the transmission are bored
completely through the housing. These fasteners must have thread sealant applied to
the threads. If oil leakage is observed at the PTO covers, replace thee PTO cover
gaskets and thoroughly clean the fasteners and their mating threads before reinstalling.
6.
Check the cover plates and manifolds bolted to the transmission housing for
cracks or breaks, including the front bearing cover plate, front housing, shift bar
housing, rear bearing cover, and the clutch housing. All of these components can
be a source of oil leaks.
7.
Check the front bearing cover plate. Oil return grooves that have been damaged
by contact with the input shaft can cause oil leakage. If the grooves are
damaged, you must replace the front bearing cover. If the front bearing cover has
an oil seal installed, inspect the oil seal. Damaged or worn seals must be
replaced to prevent oil leakage; in the case of the front bearing cover seal, the
transmission will have to be pulled.
8.
An oil leak in the front bearing cover, in the auxiliary housing, or in some
housings (such as the air breather in the shift bar housing) can be caused by a
damaged O-ring in the range air shift cylinder. The damaged O-ring bleeds air
into the transmission, pressurizing it and resulting in oil leakage.
9.
If the transmission is equipped with an oil cooler and an oil filter, inspect the
connectors, hoses, and a filter element to make sure they are tight and leak-free.
10.
Inspect the oil drain plug and oil fill plug for leakage. The oil drain plug and oil fill
plug should be torqued to specification.
Always check for a plugged transmission breather when identifying the cause of a
transmission oil leak. When transmission oil is raised from cold to operating
8-12
NAVEDTRA
14050A