I assemble the trans dry, push the shaft one direction. Put a bit of silicone in the case where the shaft will be. Put a bit on the other end of the shaft that is sticking out. Then push the shaft the other way and repeat the process... Now center the shaft, fill the hole where the pin goes through with silicone and push the pin through that... In a trans that was in the car I would drain the oil and clean the afore mentioned surface with alcohol as a precursor... No leaks for me htis way... Ahhh but I remember buying a replacement shaft from a popular suplier that was .001 smaller than the one that came out, not good! ... Karl