TM 5-6115-593-12 TO 35C2-3-463-1 a. Battery Testing.  Test batteries with hydrometer. Always test a battery before adding water.  The specific   gravity   between   the   cells   should   be within 0.025.  A dangerously low point of charge indicated  by  a  hydrometer  reading  of  1.150  or less  will  cause  the  batteries  to  freeze  at  5°F  (- 15°C).  With specific gravity of 1.280 the batter will  withstand  temperatures  as  low  as  -65°F  (- 53.88C)    without    freezing.        An    acceptable hydrometer  reading  of  1.270  to  1.280  at  80F (26.66C)  will  be  obtained  from  a  fully  charged battery (2.2 to 2.4 volts DC per cell). b. Replacement.  (See figure 4-9).  (1) Disconnect both   battery   negative   cables   (2   and   5)   both positive cable (3 and 4) and both jumper cables (1) from storage batteries (10). (2) Remove  the  eight  nuts  (6)  and  washers (7) and remove the four battery hold-down channels  (8).    It  is  necessary  to  remove studs (9). (3) Lift batteries out. (4) Reinstall  batteries  in  tray  (install  so  that terminals are oriented as shown). (5) Install  the  batter  hold-down  channels  (8) onto  studs  (9)  with  washers  (7)  and  nuts (6). (6) Connect cables as shown in figure 4-9. Section IX.  MAINTENANCE OF MUFFLER AND EXHAUST 4-17.  GENERAL.  The muffler and exhaust, figure 4-11, expel  engine  exhaust  gases  from  the  engine  manifold through     the     turbochargers,     metal     exhaust     hoses, mufflers,  and  out  through  the  muffler  rain  caps.    The rain caps include a balancing device for counterbalancing rain cap opening and closing. WARNING Be   sure   that   the   exhaust   is   not   fed back into the system, or back into the immediate  area  of  working  personnel. Exhaust may be injurious to health. 4-18.      MUFFLER   AND   EXHAUST   REPLACEMENT. (See figure 4-11). WARNING Allow exhaust pipe and muffler to cool if engine has been running. a. Remove   the   eight   screws   (1),   the   eight   split lockwashers (2) and the eight hex nuts (3). b. Remove  the  four  screws  (5)  securing  the  front mounting   brackets,   the   four   split   lockwashers (6), and muffler (8). c. Remove rain cap (7) from the muffler (8). d. Separate   and   remove   the   upper   and   lower gaskets (4). e. Remove the eight screws (9), lockwashers (10), and  nuts  (11)  which  attach  metal  exhaust  hose (12)  to  exhaust  elbow  (16)  and  remove  metal exhaust hose (12). f. Remove gasket (14). g. Repeat steps a.  through f.  for the other side of the exhaust system. h. Reassemble gasket (14) between exhaust elbow (16) and metal exhaust hose (12). i. Install  eight  screws  (9),  lockwashers  (10),  and nuts (11). 4-37