This magnetic drain plug will help keep the badness of metal shavings from circulating in your gear oil. 

It can be installed in the transmission, transfer case and both front and rear differentials on any year truck. Low profile allen key head keeps it from dragging on the rocks, so there won't be an issue removing it when you have to change the gear oil. 

OE part. includes crush washer to keep the fluid in the place it should be.