OK, was exploring the firetruck. It's like a scavenger hunt, weirdness to be discovered all around. One thing is the t-case has no shifter, so I assume it's just a single speed torque splitter.
Seems to steer OK for not having hubs and always being in 4WD. In the pic below, I figured out what the object to the left is...a power brake booster. It has a vacuum line coming from the intake manifold and two brake lines going out. They tie in to the brake lines near the wheel and, I guess, just add a bit of pressure. Brakes work well, and thank god, cuz where am I going to find parts?
Another weird think is that it's a 79 but has 4 wheel drums, and I think the earlier engine because the hood is flat. Anyway, I love the brake booster. It's unnecessarily complicated, weird and mysterious. I just hope it never "brakes".