I have an 02 F-150 with a 5 in lift and I am herding a grinding noise in what I think is in the rearend.The other day I drained the lube and replacement ed it with Royal Purple. This helped some but still hear it. When starting from a stop and turning left or right,but not pulling away from a stop straight forward.And it was a lot worse when I am towing. Can someone help with this Thanks Joe