1998 fld 120 wontg start slow crank

i have a 1998 freightliner fld120 n-14 plus not a (red top) batterys are 2 years old it is 30 degrees outside, it wont start very slow crank dont think its making even one revolution, load tested all 4 batterys, they showed between 878 and 940 cold cranking amps under a load , batterys read to be 950 Cold cranking amps, and 1140 crankig amps, cables look ok some corrosion (green) but easily removed with a wire brush, yet truck will not crank over, need ideas its only getting colder, very tight on funds. how do i check the starter on the truck...... Thank you Brian S

 

i have a 1998 freightliner fld120 n-14 plus not a (red top) batterys are 2 years old it is 30 degrees outside, it wont start very slow crank dont think its making even one revolution, load tested all 4 batterys, they showed between 878 and 940 cold cranking amps under a load , batterys read to be 950 Cold cranking amps, and 1140 crankig amps, cables look ok some corrosion (green) but easily removed with a wire brush, yet truck will not crank over, need ideas its only getting colder, very tight on funds. Thank you Brian S

 

how do i test the starter ON my truck, batterys Load test good all 4, very very very slow crank its 30 outside only getting colder, SLOW CRANK NO START