I haven't done the Ex's seals, but did them on another truck. I was amazed how solid I had to tap them to get them seated. I think the key is finding a socket, heavy wall pipe, or cylindrical anything that fits the seal housing outer diameter almost exactly to use to tap it in with. Ensuring the seating area is free of rust and corrosion with emery paper is good. A little film of gear oil is good to aid also.