Maybe I should not of used the term grease, but more like a spray lube that will wick into the hinge.
This probably wont thrill the 78 up owners but build quality on the 76/77 from all my cars and the ones ive seen was actually better on the 76/77. Im saying build quality, not the poor fender material that caused the rust issues. The 78-s simply used better fenders, more seals and splash guards to keep moisture displaced, compare the inner fender splash shield used on the the 76/77 vs the 78 up and some even used both as they do interconnect at the base. Then look at all the added plastic parts used on the 78 up in interior and the tail lights to save costs and make things more simple.
DC, the fold down seat and the 76 wagon car I have all have the 8 bolt hinge and as well a bit different hinge thats a full circle mounting point vs a easy quick install 1/2 moon like on the 78 up cars, but who knows if the later 77-s had them.
This hinge in this pic dont look bad but id not get it to move in a million years without any lube as its froze tight but WD40 and about 30 seconds and it moved freely. You might use a lube that wicks but put some paper towls under/around to catch the rusty colored fluid that it will produce.
Like in the pic, they didnt even have provisions for the 8 bolt hinge in the 78 up, why spend the time or money. But there is a not so known reason why T bar and Sunroof cars got most the fold down back seat option, the added rigidity of the lower cross brace. And it carries over to the wagons too.