Remove the two speed nuts on the inside of the cab, behind the under-hood box, allowing the under-hood box to be removed from the firewall, upon removing the 5 hex-head lag screws, from the snorkel of the under-hood box, affixing it to the firewall. This must be done, in order to access the four tiny 1/4" head lag screws on the back of the under-hood box, along with the numerous others around the perimeter of the top cover, thus allowing the box to split apart, exposing the heater core.
Perhaps this will eliminate some of the cussing! Good luck and keep us posted.
Last edited by 4-5-6 Chevy Trucks; 02/19/2012 5:56 PM.
