TM 10-3930-659-20 Table 3-1.  Preventive Maintenance Checks and Services (PMCS) (Con't). Location Not Fully Item Item to Mission No. Interval Check/ Service Procedure Capable If: 12 Semiannually Batteries a.  Clean battery posts and cable ter- (Con't) minals using a scrub brush (Item 5, Appendix C). b.  Apply a small amount of grease (Item 23, Appendix C) only around base of each battery post. c.  Test batteries for specific gravity (see TM 9-6140-200-14). d.  Check level of distilled water in battery and fill as required (see TM 9-6140-200-14).  Distilled water should be to bottom of filler neck in each cell. e.  Inspect battery cables and clamps for corrosion and tightness. 13 Semiannually Fan Belts NOTE Fan belts should be replaced In matched sets even if only one belt Is worn. a.  Check for missing, broken, cracked, a.  Belt is frayed, or frayed fan belts.  Replace if one or cracked, missing, more fan belts are damaged broken, or damaged. (see paragraph 5-37). b.  Check and adjust fan belt tension b.  Belt deflection is (see paragraph 5-37) more than 0.5 in. (12.7 mm). 14 Semiannually Front and Check oil levels in front and rear dif- Rear Differ ferentials and fill as required (see ential Oil paragraph 9-3). Levels 3-8