My parents recently bought me a 1998 4runner Limited 4x4 for my 16th birthday. When i am driving the 4runner, i hear a whinning sound coming from what seems to be the back of the car. It makes 3 differnt sounds, one when acclerating, one when coasting at like 35, and it makes a very slight whine when you just barely press the gas. We changed the oil in the rear end, but that did not seem to help. I think that i will be needing some new tires in the next few months, so that could be the problem, but if anyone has any other suggestions for fixes, please tell me. Also, when we took off the back tires, the brakes seemed to have an oily residue on them, and that doesnt seem right. I would love your imput.