1958 M56 Brake part--what is it?

[MajRJO1967]

I purchased replacement brake lines for my 1958 M56, However, there is a part installed in the system that is not familiar to me, and the replacement lines do not use this item. I have a copy of a 1950 M37 tech manual depicting the brake lines and this part is not included in the diagrams. Was this something added at a later date? Anybody know what this is, and where I can get one?

Reply to m56b1ww@yahoo.com

Thanks!
RJO

 

[Barneyszoo]

is it a proportioning valve that maybe someone added to keep the rear wheels from locking up

 

[NDT]

Mico-lock parking brake. All the G749 GMC deuces have that also.

 

[MajRJO1967]

Hmmmmm.....How does it work? How do you apply the brake, and how does it release?
RJO

 

[NDT]

It has a switch on the dash. You turn on the switch, mash the brakes, and the brakes stay applied even though your foot releases the pedal. To release the brakes, you turn off the switch. The old 5 ton wreckers have them too.

 

[MajRJO1967]

A friend and I did think it was a proportioning valve, but I thought they were adjustable? I also thought it may be a pressure reducer/increaser type mechanism, which I think is another way of saying "proportioning valve."

When I removed it didn't use double flare fittings. It was atttached using slip on nut/ferrules. The rest of the brake system was double flare, so I'm thinking this was added on lat a later date, but I'm not sure if this was an approved modification, or just a "good idea" from a previous owner (the local volunteer fire department).

RJO

 

[MajRJO1967]

M880,

Thanks, but I don't recall seeing a swith on the dash, and there weren't any leads coming from the "thing." It's a mystery, but with this truck, that's no surprise! It's been a four-year resto journey so far. Thanks for the help.

RJO

 

[Barneyszoo]

wow its kinda dangers not to dubble flair anything on the break system, Take it off and cut it in half with a band saw to see whats inside.