In the last few months I noticed that the rear of my van would make a sound of a seal (er er er er) after backed up and drove slowly forward for about a 100 ft. Then it goes away and doesn't come back until the next day or sometimes a few days later. I changed my summer tires to winter ones last week and noticed that the bottom half of the right rear shock was completely covered in a thick coat of oil. It looks as though all the oil has leaked out of the shock. I haven't replaced the shock yet but could the noise have been coming from the bad shock? Or could it be that one of the rear brakes isn't releasing right away. When I jacked up the rear of the car both right and left wheels didn't seem to spin very easy and seems to drag on the brakes. I gave the wheel a single hit with my hand and it would free up and spin really easy. Think this is normal?