I know this question isn't about a hotrod but I need a little expertice here. I'm not very familiar with this particular problem. My wife drives a 99 Toyota 4runner. The right rear is making a whining sound. Thought it might be shoes but that was a negative. The rearend is full of grease. Could it be a wheel bearing??? Do the wheel bearings on those need to be packed with grease or are they greased from the grease in the differential.