[QuantumMotorsports]

Get the cheapest underdrive pulleys you can find, In my opinion they will only make a slight difference but considering their cost, it could be worth it to you. 10-15 HP. maybe more I don't know, maybe someone's actually gone to the trouble of dynoing a car with and without them. As for the rear end, depending on where the sound is coming from and what the sound sounds like, it could be worn U joints, a screwed up axle bearing that's sloppy, a screwed up control arm bushing that's sloppy, something with your brakes, who knows, take it to a shop that will do a free inspection. Take it to more than one to see if they say the same thing. It's not really worth trying to diagnose a problem who's symptoms are a noise when I can't hear the noise. Know what I mean? It'd be like if you told a doctor "I've got this thing on my forehead, it looks weird, it's some kind of weird thing, what is it?"