Help Needed Problem with front locking hubs

[Frederex]

Only thing to do is pull the outer hub locks and clean them. I have put on new locking hubs and the grease is so thick or packed in the hubs wont unlock or lock. Only fix is to pull them and clean them out. I don't grease the locking hub part anymore with wheel grease, I use white lithem grease in a can and spray them down. I have not had any problem with them in 30 years of having 4 wheel drives. What year is your truck?

It is a 2000 f350 dually....it has a switch on the dash to engage the 4wd, but no vacuum lines to the hub assembly....the ones advertised show manual and auto available, but the look the same in the pics.