Seal replaced at the 4x4 shop. They didn't say anything else was wrong so it looks like it is case closed.

 

expansion and contraction can def cause a leak to worsen, glad you got er done

 

Here we go again. There is gear oil under the seal again. Just a couple weeks after I went back to the shop to inspect gear oil leaking out of the FRONT differential from the Posi-Lok cable. OMFG. They said it was power steering fluid coming from above the diff, but it definitely smells and looks like gear oil.