If you do split the case and replace the seals, when you put the sealant on the case halves, take a roll of sewing thread and embed a continuous piece of thread in the sealant between each shaft opening on one of the case halves. The thread is crushed between the mating surfaces, and will help seal any slightly mismated places between the halves, and help prevent seeping of lubricant from those areas in the case seams.