As a person who hasn't had much experience with rear differentials, how does one go about the tools and equipment needed for setting the backlash on my 1980 datsun 720 4x4. Reason is because when I am driving at a certain speed (about 30~35mph), i hear a roaring noise on the rear of my truck but only when I accelerate. After I let go off the accelerator, the noise is gone. I have to remove the differential either way to check it but are there other things that I should look into while I'm there?