Its not necessarily the retainer itself, unless it wasnt manufactered properly. 9 times out of ten, its the " process" itself, not the components. You will get 3 thousand different opinions on here about this subject, but trust me, its the process of getting the retainer in the right position, using the right side seals, and lining up the seal itself properly. They can be a pain. I prefer the better rear main seals, not just the stock style, but they will work also if installed correctly.The only other problem is a rear retainer that traps the oil, but thats becoming less common.