hey guys got another question i have a 98 sport with the 4.0 and auto with the np231 and while in traffic the other day and just barely moving i noticed a grrrrr, grrrrr, grrrrr coming from the under carriage. i took the front shaft off to isolate it but same thing. strange because it pulsates. any help would be appreciated. oh yea it has 173,000 miles on it