I'm a newbie so excuse me if there's already write-ups on the subject that I may have missed. I own a '99 4Runner with 141k miles. I regularly change all fluids but it appears that by not installing a $4 part and extending my breather on the rear diff I have caused the dreaded failure. My mechanic has told me to start searching for a new rear differential.... Im curious if anyone has had any luck resolving this type of issue and what the best approach would be ie rebuild or replace.