II.  LUBRICATION 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 Off-Highway Service (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 kerosene. 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. D.    Inspection Gear oil level is to be maintained at the level of the fill plug at all times.  Check at the following intervals: Highway Service..................................  1,000 miles Off-Highway Service............................  40 hours E. 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 individual’s own operating conditions.  With this data the individual    owner    can    better    determine    their    own    oil change and inspection periods. F. Operating Temperature 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. -8-