As far as i rember AFWD is the proper name for HFWD, it is just something that you would use when you are truly in the $hit, My farther inlaws 4240 has AFWD, and he said you never use it longer than 5 mins and never at more than half revs, when you do it spins the wheels far to fast( as mentioned) and it frys oild seals and stufs up basicly, was a good paper idea but crap in reality, I have been told the best thing to do with them is take them of, chuck it way and put on a real 2wd axle as it wont fry your hydrolic pumps