Found a lot of grease on bottom side of rear brake pad (inner), but none on outer pad. Thick grease that was spun out on to the mud shield. Note pix of it around back side of caliper. Caliper pistons don't appear to be leaking. Does not look like brake fluid. Very mushy grease, rubbery.

Thought on source of grease?

 

It is not grease, it is gear lube mixed with brake dust.
Check your axle breather to make sure it is not clogged.

 

That's good news Spike. So it would not be the inner seal of the wheel bearings? And the outer seal / axle shaft seal is leaking from pressure build up because of the plugged vent?

I pulled out the vent screw, and it was plugged 100%. Cleared it with various drill bits, and ran a small stiff wire up the vent hose about six inches. Blew air with another hose attached to end of vent hose under hood near ignition coils - looks like a shepard's crook. Is that the axle vent - or the tranny? Working alone not sure how to know if vent hose to engine compartment is clear.

Note grease coming out of hub on back side of brake disc. Should I clear this with a can of brake parts cleaner spray or tear it down?

 

If you removed and cleared the axle breather from the rear axle then that is the correct one.
My breather terminates under the truck, I have the tube going up the frame and curving somewhere up there.
I have to clear my breather on the axle once a year as a preventative measure.
I do the same thing, small drill bit by hand to ream it out, then carb clearner, let it dry and put it back.
No need to tear anything apart, just clean with a cleaner, like brake cleaner or a degreaser.
Again, thats not grease, grease will not leak out like that.
Check the fluid in your rear diff, its low.

 

You are correct, the rear axle vent tube comes up under the floor board - toward the transfer case. I suppose the one in the engine compartment comes from the tranny.

 

There should be 2 in the engine bay, t-case and front diff.

 

Only one on mine, will look for other, may be knocked loose. I had seen the two in salvage yard units and never thought about it..

 

Grease can leak out like that if the hub seal is leaking.
Cleaning the breather tubes and cleaning it up is the first choice though, because that may in fact be the issue.
But a faulty seal will leak grease. At operating temp the grease is quite fluid.

If clearing the breather tube and cleaning the area are done and it doesn't come back, great. If it comes back, order some RTC3511 hub seals.