So i have a 2002 Toyota sequoia with 221,000 on the clock and was having some work done on the truck this weekend. My mechanic was telling me he could hear some noise coming from the front diff.. and i was hearing a grinding noise while driving but it sounded like a wheel bearing to me. So if it is truly the front diff can these be rebuilt or just completely replace them? Also another concern i have is if i am driving and it decides to crap the bed on me while driving are the fronts going to lock up on me if i am still in 2wd?