The shutdown will affect 850 workers at the Macungie, Pa., plant, 850 at the Winnsboro, S.C. plant and 1,000 at the Hagerstown, Md., engine and transmission plant.
Macungie is currently producing 64 trucks per day; Winnsboro 72 trucks per day. Hagerstown has been averaging 160 engines per day.
The week shutdown will reduce Mack's production by 680 trucks.
A few weeks ago, Mack eliminated its second shift at Winnsboro following the annual two-week vacation shutdown. Mack also added a third week off following the two-week vacation break.