The cable may be broken. Pull the aluminum housing and roller (under hood, on firewall) and check. The barrrel shaped cable end on both of my 1st Gen cabs were broken. I found a new cable at Autozone for around $30. There is also an adjustment under there... in front of the fuel tank, if the cable is ok. Also may want to make sure the rear brakes are adjusted properly, if everything else looks legit.
