I have used anaerobic sealants such as Loctite 518 when putting together aluminum crank cases for 2-cycle motors in snowmobiles and it works incredible. However, it only seals gaps to something around 0.01" so your two mating surfaces have to be almost a perfect fit. It cures from lack of oxygen so if there are any scratches or nicks and oxygen can get to the sealant then it will never cure. My only concern on the front diff would be that the surfaces aren't going to fit together well enough to allow the sealant to fully cure.
Every time I've used anaerobic sealants in conditions that allow them to work correctly, they've been one of the best sealants I've ever used.
Corey