Note: For proper lubricant, refer to "Recommended Lubricants" chart page 9.
A. Transfer Case Oil Change
Transfer case lubricant should be changed on all new
transfer cases after the first 3,000 to 5,000 miles (on-
highway), or first 40 hours (off-highway); thereafter, oil
changes should be done at the following Intervals:
On-Off Highway Service.............. 10,000-15,000 miles
(Logging, dirt moving, mining and
associated operations) ..................... 500-750 hours, as
indicated by operation and contamination of lubricant.
B. Draining Oil
Draining is best accomplished after the vehicle has
been operated briefly, allowing the oil to become warm
and flow freely. Remove both drain and fill plugs and
allow housing to empty completely. After transfer case
has been drained and before it is refilled, the case
should be thoroughly flushed with clean flushing oil or
C. Refilling Oil
If the transfer case has been removed from the vehicle
for service, it is best to refill the oil after the transfer case
has been reinstalled into the vehicle.
Clean and replace drain plug and fill the transfer case
with appropriate gear oil with the vehicle on level ground
(See recommended lubricant chart). Fill transfer case to
the level of the fill plug, metering approximately 7 qts. of
gear oil into the transfer case. The exact amount may
differ depending upon the inclination of the transfer case.
Always fill to the level of the fill plug. Replace fill plug
and examine transfer case for leaks around plugs and
gasket sealed areas.
Do not overfill the transfer case. Overfilling may cause
seepage around bearing caps.
Gear oil level is to be maintained at the level of
the fill plug at all times. Check at the following
Highway Service.................................. 1,000 miles
Off-Highway Service............................ 40 hours
Oil Change and Inspection Recommendations
The above oil change and inspection periods are
based on the average use and operating conditions the
transfer case may encounter. It is recommended that
the individual owner make a periodic lab analysis of the
lubricant to determine contamination based on the
individuals own operating conditions. With this data the
individual owner can better determine their own oil
change and inspection periods.
The operating temperature of the transfer case should
never exceed 250(F (120°C). Extensive operation at
temperatures exceeding 250°F will result in rapid
breakdown of the oil and shorten the transfer case life.
G. Shift Cylinder Inspection (Air Shift Cases Only)
With every oil change the air shift cylinder lines and
valves should be inspected for leaks and possible
malfunctioning. Low pressure conditions can cause
partial clutch tooth engagement which may result in
"gear jumping" and premature wear.
H. PTO Oil Pump Inspection
Check oil pump output at: Initial installation;
reinstallation; if case over heats during extended PTO
operation; at each oil change. Disconnect PTO oil pump
output hose from the fitting at the front of the case.
Block the truck wheels, set the parking brake, put the
transfer case in neutral, engage the PTO. Make sure the
output hose is clear of the transfer case input shaft. Use
something to catch the oil. Keep hands away from
rotating (and hot) parts under the truck. Operate the
case at idle speed and observe the oil flow. Flow should
be about 10-12 oz. per minute.
If no oil flow is observed, disconnect output hose at the
output check valve (Refer to Page PM15 and to Fig. 39),
remove the output check valve, prime pump with transfer
case lubricant added through the hole exposed in the
side of the oil pump. Reconnect the fittings at the PTO
end of the case and repeat the test described above.
Refer to section VI J if difficulties are encountered.