the front diff has a mean popping going on only when it is in 4 wheel hi or lo.no prob.in 2 wheel at all.i pulled the solenoid out and it seems to accuate properly.any ideas? diff oil was black in sol tube.but didnt stink any more than usual. thanks for any help. going to the deerlease on november 3rd the 4x4 will be used if opp.