An improperly operating clutch will interfere with the
proper shifting of gears in any transmission. It is also
important that the hydraulic, air or similar release
mechanism is In proper working order. If full and
complete clutch release is being made, the following
could be a few of the possible causes for hard shifting
(a) No lubricant in remote control unit. (Note The
forward remote is isolated and is often overlooked.
Many remote controls used on transmissions and
auxiliaries require separate lubrication.)
(b) No lubricant in, or grease fittings on, u-joints or
swivels of remote controls.
(c) Lack of lubricant or wrong lubricant used, causing
buildup, of sticky varnish and sludge deposits on
splines of shaft and gears.
(d) Badly worn or bent shift rods.
(e) Improper adjustment on shifter linkage.
Sliding clutch gears tight on splines of shaft.
(g) Clutch teeth burred over, chipped or badly mutilated
because of improper shifting.
(h) Binding or interference of shift lever with other
objects or rods inside the cab or near the remote
Driver not familiar with proper shifting procedure for
the transmission, or with 2-speed axle or auxiliary.
Clutch or drive gear pilot bearing seized, rough, or
(k) Clutch brake engaging too soon when clutch pedal is
Wrong lubricant, especially if extreme pressure type
lubricant is added.
(m) Free running gears seized or galled on either the
thrust face or diameters.
Sticking in Gear
(a) Clutch not releasing. Also check remote units such
as hydraulic or air assist. Note: On some units
employing a full air control for clutch release, air
pressure of approximately 60 lbs. or more must be
secured before the clutch can be released. Do not
leave these vehicles parked in gear.
(b) Sliding clutch gears tight on splines.
(c) Chips wedged between or under splines of shaft and
(d) Improper adjustment, excessive wear or lost motion
in shifter linkage
(e) Clutch brake set too high on clutch pedal, locking
gears behind hopping guards.
The service life of most transmissions, main and
auxiliary, is governed by the life of the bearings. The
majority of bearing failures can be attributed to vibration
and dirt. Some other prominent reasons for unit bearing
(a) Fatigue of raceways or balls.
(b) Wrong type or grade of lubricant.
(c) Lack of lubricant.
(d) Broken retainers, brinelled races and fretting caused
(e) Bearings set up too tight or too loose.
Improper installation resulting in brinelled bearings.
(g) Improper fit of shafts or bore.
(h) Acid etching due to water in lube.
Vehicle overload or too large an engine for the
transmission resulting in overload.
More than 90% of all ball bearing failures are caused by
dirt, which is always abrasive.
Dirt may enter the bearings during assembly of units, or
may be carried into the bearing by the lubricant while in
service. Dirt also may enter bearings through seals, the
breather or even dirty containers used for addition or
change of lubricant.
Softer material, such as dirt or dust, usually forms
abrasive paste or lapping compounds
bearings. The pressure between the balls and raceways
makes a perfect pulverizer: The rolling motion tends to
entrap and hold the abrasives. As the balls and
raceways wear, the bearings become noisy. The lapping
action tends to increase rapidly as the fine steel from the
balls and rollway adds to the lapping material.
Hard, coarse material, such as metal chips, may enter
the bearings during assembly from tools such as
hammers, drifts, and power chisels. It may also be
manufactured within the unit during service from raking
teeth. These chips produce small indentations in balls
and races. When these hard particles jam between the
balls and races, it may cause the inner race to turn on
the shaft, or the outer race to turn In the housing.
All bearings are subject to fatigue and must be replaced
eventually. Your own operating experience. will dictate
mileage replacement of bearings showing only normal