[Gregski]

please help, in my 74 2WD GMC 1/2 ton when I step on the parking brake pedal it won't stay engaged, (sometimes it does, maybe once in 20 tries) the other times as soon as I take my foot off of it the pedal comes back up

when I look under the dash I can see there are little teeth on a black metal bracket that the pedal moves but I can't see what is supposed to drop into them to engage

please advise