Wheel seal or axle gasket

Some of them have allen head plugs in the hub, if you had them done recently maybe the mechanic didnt clean the threads on the hub plug.

 

The Allen plug would leak on the outer wheel. I would either steam it off and see if it comes back or pull the wheels and air test it.

 

Been 7 months since ive done breaks lol thanks buddy

 

I thought the same thing you did at first........so I went and looked at one. It's about an inch outside the wheel.

 

I put three wheel seals in an Astro with a 8V71 once before I figured out it was not the wheel seal. The oil slinging 71 was was doing it. Some how air currents blew oil into that one drum.
Just saying thank outside the box. Some vehicles had a shield to carry oil from a seal outside the drum. Do not that that would be on your truck.

 

He needs to check his axel vents!

 

That is a good point but I do not thank that is his deal.
We had several 388's with leaking axle flanges over the years. Probably from the transport company that decked them.
Recently we had one with oil between the wheels as mentioned. Right side front and rear axle. That truck has a hydraulic pump that can run three different applications. One is for an end dump that we are not using but the end tied above the right frame rail was wet. We discussed it. Replaced the end on the hose. Knocked out both the axles and resealed them. That is not any money to spend as to what it can cause on the road. No more oil on wheels.
I do not see how an axle flange or the plug you mentioned could put oil between the wheels. Ours did have a little oil in the outside rims but not like the previous flange gaskets. That fixed our problem.
We are getting hammered. Tag lights, farmers hauling hay, 2500 with trailer requires DOT # ,not for hire?
Spend a little extra at home and save a lot on the road.