While traveling down a hill, about 40mph, applied brakes to stop at a T intersection, truck wasnât slowing down. Engaged engine brake, truck wasnât slowing. Slammed brake pedal to the floor, ABS did not engage, no vibrations, wheels didnât lock up, held for 2-3 seconds then started to release and slam brake pedal repeatedly. Truck went through intersection, hit a lot of trees, dropped down a 6â embankment, air bags did NOT deploy, trucks frame bent on both sides behind the cab.