5. Install  the  7  5/8"  overall  length  underdrive  shift  fork (Item    35);    it    should    fit    into    the    groove    of    the underdrive shift clutch (on the intermediate shaft) the long  hub  section  should  be  facing  the  rear  of  the case.  Insert the two-groove shift shaft (Item 36) into the  adaptor  tube  (Item  15)  at  the  rear  of  the  case housing  (see  1  of  this  section).    Slide  end  of  shift shaft into underdrive shift fork (Item 35).  Put 5 7/8" overall  length  shift  fork  (direct  drive  shift  fork-Item 34) long hub toward front of the case,  into  the  case with the forks in the groove in the direct drive clutch on the input shaft.  Push shift shaft through this fork (See Fig.  35) and into the hole in the front wall of the case  housing.    Push  on  the  end  of  the  piston  and compress the spring until the piston butts against the nylon  stop  ring  and  the  adaptor.    This  will  allow  the set screw in the underdrive shift fork (Item 35) to be tightened  into  the  proper  groove  on  the  shift  shaft. Rotate  both  shift  forks  in  either  direction  but  in  the same   direction   and,   with   the   second   fork   in   the proper   place   longitudinally,   tighten   set   screws   to specified torque and install the lockwire. Fig.  35 6. Place the forks of the front drive shift fork (63/4" long overall   Item   16)   in   the   groove   in   the   front   drive clutch.  Insert the front drive shift shaft (shaft with a single groove for the single shift fork Item 12), spring (Item 14) and nylon stop ring (Item 13) into the shift cylinder  adapter  previously  installed  in  the  front  of the case housing.  Pass the shaft (Item 12) through the  shift  fork  and  into  the  hole  at  the  back  of  the case.    Rotate  the  shaft  to  position  the  longitudinal groove   away   from   the   indicator   light   switch   hole. Push  on  the  piston  enough  to  put  the  groove  in  the shaft  under  the  set  screw  in  the  shift  fork.    Tighten the set screw to specifications and lockwire. 7. Soak  the  air  shift  piston  felt  washers  (Item  10) with gear oil and install in the shallow groove  of the piston (shift shaft side of piston).  Install the shift  piston  o-ring  (Item  8)  in  the  deeper  groove on the pistons (Item 9).  Oil the rings. 8. The shift cylinder tubes are of differing lengths.  The shortest  tube  (Item  4  which  is  3-1/16"  long)  should be slipped over the front axle shift piston on the front of the case.  The longest shift cylinder tube (Item 37 which is 3-13/16" long) should be fitted over the high- underdrive shift piston on the rear of the case. 9. If the transfer case is equipped with a PTO unit, the case   must    have    a    neutral    position.        Neutral    is obtained  through  the  use  of  a  "piggy-back"  cylinder mounted   on   the   high-neutral   cylinder   (see   Page PM7).  This "piggy-back" cylinder, when actuated by properly  connected  air  valves,  provides  this  neutral position.    The  "piggy-back"  cylinder  consists  of  an adaptor   (Item   41)   into   the   grooves   of   which   are installed oiled o-rings the  adaptor  may  be  put  either end  first  (it  is  symmetrical)  into  the  end  of  the  high- neutral shift cylinder tube (See Fig.  36).  The air inlet connection   should   point   in   the   same   direction   as when  removed.    The  "piggy-back"  shift  shaft  piston assembly  (with  nylon  stop  ring  over  the  end  of  the shaft)  should  now  be  inserted  into  the  "piggy-back" adaptor.      Slip   the   "piggy-back"   shift   cylinder   tube (Item 43 which is 31/e" long) over this piston. 10.  Insert  o-rings  in  cylinder  caps,  install  cylinder  caps on cylinder tube open ends.  Fasten to case housing with  the  appropriate  bolts  (Item  5  or  38)  or  studs (Item 44) and nuts (Item 45). 11.  Install  plunger  (Item  22)  into  the  front  drive  switch hole  with  the  rounded  end  toward  the  shaft.    Install the  shift  indicator  switch  (Item  20)  with  one  copper washer   (Item   21).      Test   switch   operation   with   a circuit tester while shifting into and out of front drive. Add   washers   as   necessary   to   make   the   switch operate properly. 12.  Cover exposed end of shifter shafts with the gaskets (Item  23)  and  covers  (Item  24)  provided.    Secure with 4 bolts (Item 25) each tightened to specifications. Fig.  36 -24-