THIS FAILURE WAS THE RESULT OF A REAR UND COLLISION WITH MY VEHICKE STOPPED. THE VEHICLE THAT HIT MY TRUCK WAS A SMALL IMPORT TRAVELING AT ABOUT 40 MPH. UPON IMPACT MY HEAD WAS SNAPPED BACKEARDS AND ACTUALLY WENT THROUGH THE REAR WINDOW, SHATTERING IT AND CAUSING A CONCUSSION SEVERE ENOUGH TO CAUSE ME TO TO BE UNABLE TO CONTINUE TO WORK. THERE WAS NO HEAD RESTRAINT OR BUMPER OR PAD EXTENDING HUGH ENOUGH FROM THE BACK OF THE SEAT TO CUSSION THE HEAD. LATTER MODLES (IE 1992) HAD AN EXTENDED HEAD REST. GMC SHOULD HAVE RECOGNIZED THIS PROBLEN AND OFFERED A REPAIR ABOUT THE SAME TIME IT REDESIGNED THE BENCH SEATS TO INCLUDE A PASSIVE HEAD RE