December 22, 2008.
Dear DRJCONLEY:
Take a look at the -20 and -30 manuals for the M35A2 to see the systems set up. The Army was, for 1948, eminently logical on the deuce's brake system, inasuch as they needed power assistance to make them work, they needed to be able to move the truck quickly in emergencies without having the air build up, and they had to be able to tow them quickly also in an emergency.
If they were straight standard air brakes, any damage to the air system or time delay in building up the air, might concieveable in some circumstances, loose the truck and the load.
EG: Enemy attack shoots off an air line, or enemy attacks motor pool or convoy when the trucks have been shut down, brakes are locked, truck's immoveable, or unstoppable, depending on what happened..... The hydraulics work the brakes from the pedal and master valve, the airpack senses pedal inputs and assists in pushing the master cylinder to the apply position. The airpack serves the same purpose as the vacuum assist on most other modern car and truck brake systems.
The only weakness in an unmodified (to ESP standard M35A2) is the loss of any hydraulic line is gonna render the truck almost uncontrollable, hence the splitting of the hydraulics in the rebuilt M35's in the 1980's and almost all AF M35A2's.....
Basically, if the M35's working right, it takes less effort to stop it on my part as the driver, then my 1963 Swiss Unimog, which is much smaller in size, but with no assist to the hydraulic system..... A Unimog S404.114 in heavy traffic is a tiresome beast to have to stop, a Deuce is a tiresome beast to have to shift.....! Due to the sensitivity to failure of the hydraulic systems on the M35A2, it is essential that they be inspected and maintained to a higher standard then other vehicles in terms of preventative maintenance, as the parking brake WILL NOT STOP the truck, and neither will most telephone poles or trees if the truck has any momentum built up. I hope this will help you visualize the operation of the brakes, as they are different then any other truck's before or since.
Have a Safe and Happy Holiday Season,
Cheers,
Kyle F. McGrogan