A common leak on the rear axle is the axle seal. This can be identified by smoking and burning oil smell from rear brakes. It may be noticed by grease and buildup on the backing plates as well. If left alone, it can saturate the parking brake shoes and inhibit parking brake operation. If it leaks bad enough, it can get on rear pads and cause dangerously poor stopping performance.
One seal required per side
Updated Rear Axle Seal11.5"