just had all my fluids change @ a quick lube shop, Now when I drive on the interstate I hear a slight roaring noise coming from the back of the VX, I checked the manual and it says that rear axle needs an additive that I dont think was put in. Could this be the cause of the roaring noise that WASN"T there before the fluid change.And can I get both these fluids @ St Charles isuzu? Any help would be appreciated