The Stovebolt Site Forums The Parking Lot Big Bolts 55' 6400 Rear Brakes

The last thing I have to do before I attempt to drive her home is get the brakes working again. The master cylinder was dry when I opened it up. The pedal goes to the floor yet the rear brakes are stuck so she won't roll. My friend John freed the fronts and everything looked good there. He suggested that the system must have pressure either air or hydraulic, for the rear drums to return (like a Big Rig). I am pulling the M.C., but so far we are stumped.

Also, does anyone know the what brake system I have in this 55' Chevy 6400 with a 2 speed rear, 4 speed manual with the e-brake drum? There is a canister that looks like a vacuum unit mounted in the middle of the passenger side frame rail where all of the brake lines run into as well as vacuum lines to and from the engine.

No pressure needed to return the shoes on the hydraulic brakes on your 55 6400.

When working the springs retract the shoes when you release the brake pedal. Just like normal drum brakes on most cars and trucks.

Likely the shoes are rusted to the drums.
Have you tried driving it, they may brake free if you try?

Grigg

The vaccum unit is probably an old Bendix Hydrovac brake booster.

Ditto on the Hydrovac. Your brakes most likely are vacuum assist fluid brakes. If by some fluke you had air brakes, you'd have a compressor on the side of the engine, and prob. a brake release knob in the cab.

I agree that the cannister you found is a vacuum canister, meant to assist the braking and store a little vacuum for a few stops if the engine quits.

Rear brakes use return springs like the front. Don't know the history of your truck, but these springs definately rust and break.

On the other hand, my '44 sat for just two years (inside), and had stuck rears. We pulled the drums (with a lot of effort) and the springs were fine. I think the hubs/brakes just get crudded/moistured up and freeze. Not much to lose by "jarring" them loose somehow - you may avoid having to pull the hubs (lots of work).

Of course, unless you're only going a short distance, it would be prudent to rebuild all the brakes and re-grease the wheel bearings, anyway . . . (what with all the spare time you have, yes? ;-)

-Michael

Here are some pics of the progress. I pulled it back and forth out of the barn and freed the rear wheels. We had pretty good luck getting the drums off and pulled all of the wheel cylinders in the rear. I am going to have to get some new ones and a new master cylinder, they are kinda rusty and pitted. Here are a couple of shots with the wheels off, it looks pretty clean under there. The engine could use some TLC but she starts and runs now after a long 20 year nap.
http://photobucket.com/BriteFab

Good luck with your brake issue that is a really nice looking truck not many 6400 had deluxe heat and radio options them are really cool in them self.

While your fixing the brakes don't forget to replace ALL of the steel and rubber lines. The old lines fail from the inside out. The steel lines rust and the rubber lines swell. They are cheap and easy to do. When done everything will be new and you won't need to worry for years to come. You might have trouble finding a "new" MC, but you can send your's out and have it sleeved if it is pitted bad. Then add a NAPA rebuild kit and your back in business.

Good luck!

Mike B