4x4 problem

[futbal2332]

Its not a powerstroke by my uncle has a 01 f150 triton 5.4 with electronic 4x4 that wont go in 4x4, over the summer we were pulling the boat out of the water and when he put it in 4x4 high it grinded and he hasnt needed it since, well we got a snow storm the other day and he said he put it in 4x4 and the lights came up and all but never locked in, he needs the 4x4 to get up his driveway and we have another big snow storm coming on tuesday, im not to familier with electronic 4x4 so a little help would be good, could it be a solenoid or a moduale or something, and are they easy to replace? sorry for posing on the powerstroke forum but you guys are usually quick with answers and help, thanks erik