There's multiple schools of thought on how to pack a knuckle. Some guys wanna fill it up with grease, some use barely any. I like to grease all the surfaces well and throw in a healthy glop or two for good measure. I definitely don't pack it 3/4ths full though, but that's me. I wouldn't overthink it. Throw some grease in there and get back to driving.
Also, you have a stupid clean truck and I don't like you. Go scratch it up please so I won't be so jealous.