[RalphG]

Can't speak for Ford but I know my 59 IHC pickup has a locking differential with the tag on the dash indicating "Power-lock differential) It took a special fluid for refill too. I think I still have a can of it here. A Chryco product. I found the power lock differential to be a little "squirrely" on muddy roads. It would spin both wheels and that tended to push the truck in directions I might have been intending to go. I recall one episode of sliding off the muddy road and shearing the top off a big anthill before spinning back onto the road and resuming my journey.