The headline number fell to 42.0 from 49.6 a month ago.
Any number below 50 signals contraction.
The production sub-index tanked to 37.7, down 12.5 point from July.
The employment sub-index fell 4.2 points to 42.7.
Meanwhile, the input price index surged to 70.9, up 14.5 points.
The wage index spiked to 68.7, up 14.9 points.