4wd won't work

I put my 95 ranger4x4 in 4 wheel on a hill and it made a loud thunking noise, it tryed to work but it seemed like the auto locker is slipping,is that possible? I have a 84 parts truck it has man lockers on are they interc hangeable?

first you need to find out if it's your transfer case or your lockers.i know you can put manual lockers on it.check part numbers on both years for an aftermarket locker to see if they are the same. it could also be the ring and pinion gears. 10 years of abuse on a front axle anything is possible.