the 4 wd on my 95 limited is engaged by a dash mounted switch, ie 2wd, 4wd auto, 4wd low. it always engages ok but is usually troublsome getting back into 2wd, i looked underneath and can see a 4 inch round posible solenoid mounted on the front wheel axle and it appears loose, moves 1/2 inch by hand is this what needs to be serviced. i am replaceing the front drive axle universals this weekend and would like to inspect this device if i knew what to look for. any suggestions ??