fluids changed

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

You can purchase LSD Addititive at any automotive store. Try a Kragen/Autozone/Advance/Napa and they'll set you right. It costs about $10 a tube, and you'll only need one.

If you use the Isuzu brand, you need 2....

I never knew there was an "Isuzu" brand -should I be using this instead?

I've been using the Mobile 1 and the Shell stuff.