Picked up a 77 f-150 custom yesterday. It's in pretty great shape mechanically except the 4wd is acting up. when engaged it begins a hop on the front end. Any ideas? It is a 4 speed manual with granny. Snow is starting to fall here in colorado and although this isn't my daily driver it would be nice to have 4wd fully functional. For those curious, my daily driving is an expedition lifted 6 inches with 37's. will post a picture of both rides.