My 2002 F-150 4.6 4X4 with floor shifting 4WD sometimes works. Some days the thing works fine and some days you pull it into 4 hi and nothing happens, and sometimes you can pull it into 4 lo and the 4X4 light on the dash comes on and it is in 4 lo but the low range light does not come on. I am sure the transfer case is engaging because that is manual. There is nothing constant about when it works and when it doesn't, does anybody have any ideas????