Hi Guys, I just returned from a 1400 mile road trip in my '99 D1 to Southern IL and back. I didn't notice this when I stopped for gas the last stop before home but when I looked at the truck this morning there were oil spots all over the rear end. I looked under the rear and saw some seepage from the rear axle hub but nothing significant, then I noticed the right rear wheel wet with oil or grease around the center on the inside. Any suggestions? At first I thought of a wheel cylinder leak but the brakes are fine and don't pull to one side. I suspect a wheel seal leaking diff oil. Let me know your thoughts. Is this common? Is it difficult to replace if it's the seal? Thanks in advance for your input.