There is a TSB (old one) that recomends that the ****** be coated with anearobic sealant before it is installed. You should also be careful when installing the axel so as not to damage the seal as you slide in the axel.
Also check the axel for any rough surface caused by corrosion and/or any burrs or nicks that could damage the seal. Lubricate the seal with grease if it does not have any on it. Then lubricate the axel with the trans fluid before sliding it in. rangerj