Pettibone Multihoe LDA brakes

[clwhitt]

I've resurrected a 1968 Pettibone Multihoe LDA backhoe that has been sitting on my property for probably about 10 years. Its Detroit Diesel 3-53 fired up right off the bat (after a round of preparatory repairs/searches for replacement parts), and has been a series of repairs to old parts since then (hoses, tie-rod ends, steering column, etc. - though it has also proven very useful in between repairs). But I really need to do the brakes, and, honestly, I have never seen this type of setup before (I am a very capable mechanic, just never worked on tractors before this).

The brakes appear to be air brakes, two adjacent pedals on the floor that exhaust air when depressed - I don't know what these pedals operate (uh, right now, they operate nothing). There is an air reservoir below, as well as a component that looks to be a compressor. I see brake shoes in the drive/transmission coming off the motor (drive line brakes?) and brake lines going to the rear wheels. There is no sign that there are brakes on the front wheels (no brake lines). There's also a manual handle that I assume is a parking brake (haven't fully investigated/traced this yet)

So my question centers around the brake pedals - does one pedal operate the drive line brake, and the other rear wheels, or are they differential braking on the rear wheels? I don't see a master cylinder for the brakes - are air brakes strictly all "air", no hydraulic component? Finally, the big question, replacing the brakes, just how difficult is it (a broad question, I know, broad answers are OK)?

This was my first post, so let me say in advance, thanks, it's good to meet you all.

Chuck, from the soggy, and great, Pacific North "Wet".

 

[Stimw]

The drive line is probably the parking brake and the rear, service brakes.
Two foot peddles should be right and left.
Air brakes normally are air only and fairly simple until the government got involved in the late 70's. Much better overall but complicated.
YEARS ago they used Vacuum Brakes on semis! I have seen them on very old equipment no longer in service.
Air should only leak when you let off the peddle as in letting the pressure off after stopping.
Is the compressor putting out air to the tank?
Just googled and they are air over hydraulic brakes. Her is more info for you to look at- Google

 

[clwhitt]

The drive line is probably the parking brake and the rear, service brakes.
Two foot peddles should be right and left.
Air brakes normally are air only and fairly simple until the government got involved in the late 70's. Much better overall but complicated.
YEARS ago they used Vacuum Brakes on semis! I have seen them on very old equipment no longer in service.
Air should only leak when you let off the peddle as in letting the pressure off after stopping.
Is the compressor putting out air to the tank?
Just googled and they are air over hydraulic brakes. Her is more info for you to look at- Google

Bringing the thread up to date, I pulled the master cylinder (a typical automobile hydraulic unit) and it was absolutely full of "gunk". I took it to my local NAPA store and they were able to identify it by the stamps on the body (a Wagner Lockheed unit that cross-referenced to a master cylinder for a 1956 Ford F-350). It was absolutely identical in appearance (well...except for the rust, oil and dirt ;-) ). Bolted it on and "bench" bled the master cylinder using the piston driven by the air cylinder, but at this point, I am unable to open the bleeding valves on the wheel cylinders, so I'm still without brakes. I'm sprayed the bleed bolts with Aerokroil (my favorite penetrating oil) and am waiting to see if that works. Given the "gunk" I found in the master cylinder, I'm betting that same crap has filled the wheel cylinders. I'm dreading having to take those big *** wheels off, but that may well be the next step.
Thanks for your help so far, that link was valuable.