The whole assembly is not sealed to the differential/trans with a gasket, just a round seal is used with about a 1 1/2" id that the axle from the assembly goes through in to the diff/trans. You can take it apart as you questioned about if you want to check the bearings and bull gear, but the whole thing must come out to get to the brake drum.

I got the truck block up this weekend so I can work on it. Looking under it it looks just like you said mrfixit. Its leaking where the hub assemble mates up to the diff, I assume its leaking into the hub assy hence the brake issue. I'm guessing that its the those bearing support assy seals that are leaking?

I assume there is not a seal between the hub assemble and the diff because it should be dry in there. Is that a good assumption?

Another question I'm thinking about checking the wheel bearings and other seals so I'm looking to disassembling the whole thing instead of pulling out whole. Is there any problem doing it that way?

I don't have a good bench so it would be easier to remove piece by piece instead of removing whole then disassemble.

I took some pictures but I couldn't figure out how to display them. I don't know if the forum allows pictures.

Special tools aren't required- just more time than usual for a brake job (I quote this type of job at 8 hrs when doing it on the street by myself). The brake assy's are inside the hubs that support the drive wheels. There are a series of nuts on the front of the rear assy (behind the upright) that need to be removed as well as bolts inside the wheel well (3/4" head). Once these fasteners are removed the hub & wheel assy's slide out w/ the brake assy's attatched. There are covers on top of the hubs that give access to the brake line connections which need to be disconnected first before removing the hubs

Make sure the lift is supported properly before removing the wheels & be sure to replace the axle seal & O-ring in the differential support bearing assy. IMHO- getting the bearing support out of it's housing is the most frustrating part of the job- be ready to sacrifice a flat head screwdriver or 2- bending the tip at a right angle to get under the lip works.

Be prepared to loose a good bit of ATF when the hubs are pulled & even more when the bearing supports are removed. Fill w/ the latest Dextron when the job's complete & you should be in good shape.

I have a leak at the front of the truck I have eliminated the mast cyl and line. This weekend I cleaned the top of transmission and drive housing. There is nothing leaking on top. I say that to say is it possible I have a leak on that inner seal into the hub assemble affecting brakes as well as leaking on the ground.

Second question I,m an experienced mechanic with a good array of tools. I'm not an experienced lift mechanic. Is this something I could reasonable do? Do I need specialized tools?

Petal going down 1/3 and hard but not stopping unless you stand on it is a problem with friction of the brake shoes. They are probably oily. That's kind of a big job to get at brake shoes being that you have to remove the whole axle end assemblies. Fluid shooting up with the cap off the master cylinder is normal. Empty inching cylinder means that it leaks or the inch valve slave is leaking. Bubbles coming up after filling is just it's trying to bleed itself. I think you need to get at the brake shoes to solve the problem.