MACK issued a recall on the GU model

Certain vehicles may have been assembled with an incorrectly manufactured Bendix MV-3 dash control valve. If the double check valve becomes lodged, in the event of a primary reservoir failure, air pressure can leak past the lodged valve, thereby depleting the secondary reservoir, causing a reduced ability for modulating the emergency brakes. Extended stopping distances may result in a vehicle crash, causing property damage, and/or personal injury or death. Correction: Dealers will inspect and, if necessary, replace the dash control valve.