Last week the temp was -17.I warmed up my truck,put in gear (manual tranny) and it would not move,the rear end must have gotten water in via the breather tube at some time.As soon as the temp was above freezing I was able to drive the truck with no problem. I wan't to drain and fill with new grease,but I can't remove the plug. It is located on the right front side on the diff.and I can't find the correct allen wrench to get it out. Is there a ford tool needed,or does it take an odd size ? It is hard to see the plug . Thanks Bob in Wichita.