TM 10-3930-671-24 Service Brake Adjustment (Continued) 2. Adjustment thru Wheel Hub Openings    in    the    wheel    hub/brake    drum    have    been provided   for   easier   access   to   check   and   adjust   the service brakes from the outer side.  Requires removal of drive wheel and tire assembly.  Some models may have only a slot for measuring brake clearance; adjustment is made through the plug openings on backing plate. Later models have a slot and circular opening for access also to  the  adjustor.    The  opening  is  enclosed  with  a  dust cover held in place by a single screw. 1. Remove   wheel   and   tire   assembly   from   wheel hub. 2. Remove   dust   cover   from   access   opening   in wheel hub/brake drum. 3. Use   a   feeler   (thickness)   gauge   to   check   the clearance between each shoe and drum.  Use a screwdriver    or    equivalent    tool    to    rotate    the adjustor ratchet wheel in the brake. 4. Use a tool with a hook to pull on and release the ratchet  pawl  when  it  is  necessary  to   back   off adjustment (increase clearance) of the brake. IMPORTANT-  Do  not  overtighten  brakes.    It  is  very difficult to release the ratchet wheel pa  wl  and  back off adjustment of the brake. 5. Carefully adjust clearance between brake shoes and   drum   to   .010-.012   in.      (0.255-0.304   mm) measured at slot opening.  Move slot by rotating brake   drum   to   check   clearance    at    positions shown by Fig. 4, J.  Service  Brake  Adjustment on each brake shoe. 6. After   adjusting   brakes,   install   dust   cover   over access opening in wheel hub. 7. Install   wheel   and   tire   assembly   on   drive   axle wheel hub. 8. Install  wheel  mounting  lug  nuts  and  tighten  to torque spec:  470-530 lb-ft.  (637-718 N•m). F-378