5ton CTIS valve popoff and drip

[olewhiskey]

Left rear axle outer leak but gear oil leaking from Ctis fitting any ideas if this is just outer seal or something else. From android

 

[Suprman]

The ctis system flows air through the hub if those seals go bad I think hub lubricant can get into the valve and tire. The fitting would have to be loose for lube to come out of it. Post a pic.