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I'm looking at trying to figure out as much info on 55-66 chevy gmc semi trucks and their brakes. any info is much appreciated. I would like to find one of these truck to use to haul grain. i don't have a long haul and i think it would be pretty neat. I would try and get an older grain trailer, so can you do something like that with air over vacuum brakes? or do you need a full air brake system? how does it all work? i just am not sure the oldest semi i've drove is 94 w900 thanks mike

Hy mikes 63-k10, the trucks you're asking about employed three different braking systems. Vacuum over hydraulic, compressed air over hydraulic, and full air brakes. If you are going to hook up to a full air brake trailer, the easiest system on the truck would be a full air brake system. Some of the old trucks which were equipped with compressed air over hydraulic brakes, plumbed a hand valve into the compressed air system and used it to control the air brakes on an air brake equipped trailer, this would not function automatically as would be the case if the towing vehicle was equipped with full air brakes. Earlier semi trailers were equipped with vacuum brakes, and it has been decades since I've a functioning system, hope that helps.

Not many Chevs of the mid 50's had straight air. And straight air is the only way to go if you're going to pull a trailer. Vacuum trailer brakes were almost a thing of the past by the mid 50's because they were so undependable. Most of the time you had no brakes. But those were totally different times. If a driver only piled one truck up a year, he was considered a rather safe driver. But today that is totally unacceptable. I hauled grain and gasoline with a sister to this one back in the 60's.

https://plus.google.com/photos/108197707187186692269/albums/5833890633528587697?hl=en-US

Its a 55 GMC that was born with straight air. Air valves can easily be retrofitted with modern valves and it will stop just like a new truck with the exception of not having ABS. Air brakes are actually the simplest type of brakes there is and they really haven't changed much in the last 50 years except for ABS which really only becomes a factor on slick pavement.

that is a neat truck, i'm hoping to find something about like that thanks for the info guys

My grandfather had a 47 advance design tractor with vacuum brakes for the trailer. He also said the vacuum trailer brakes were so iffy you were best to drive as if you had no trailer brakes at all.

I have a 1956 Chevy that has Air Over Hydraulic however and it has a treadle pedal. I have two master cylinders each with a air actuator. One serves the front axle and the other the rear. The set ups are also different sizes (air actuator and master cylinder), the bigger set serves the rear axle. This truck was born to be a road tractor.

Mike B

I would definitely hold out for a truck with full air brakes. Those old hydraulic brake trucks usually have a pair of wheel cylinders at each wheel, which can get expensive to have safe reliable brakes. Air is much simpler. I have a 52 GMC with air over hydraulic, I am changing it over to full air as part of the whole vehicle rebuild process.

I've had trouble with the "newer" air-brakes,as well. I had a right-front S-cam "rotate",and lock-up,but that was AFTER standing on the pedal with both feet,and pulling both the "Stops". Still ran the red-light doing 35 M.P.H.,and then catching fire(hot hub-grease).Yes,I released the brakes,but the S-cam didn't "Lock" the wheel,but caused enough friction to cause a hub-fire. 6-months later,a fellow driver lost the brakes in the same truck,and rolled it at the bottom of a long hill. luckily,the windshield popped-out,because he "Ran",with one foot out the windshield-frame,and one foot in the window,until it stopped! If you "run" with air-brakes,make sure you keep the system free of water. If it's humid,drain your tanks every chance you get. Better yet-invest in an air-dryer.

What do you mean when you said the cam "rotated"? Do you mean it cammed over or what? If this is the case, it is just plain old sloppy maintenance. Your linings are too thin and your drum is worn out and and the cam bushings were probably worn. If you ran an red light going 35 miles per hour, that means you were just plain going too fast for the piece of junk you were driving. Did the truck have automatic slack adjusters? If so, did anyone ever grease them and make sure they worked? If not, did anyone ever adjust the brakes? If you don't have automatic slack adjusters, they don't adjust themselves. I doubt that a truck has left the factory in the last 25 years without an air dryer installed in the installed. But air dryers need maintenance too. I think you should either learn about air brakes, hire someone who knows about them or just quit driving vehicles with air brakes.

I've had one brake where the s cam flipped which then kept the brake engaged and it was as ken suggested brake linings were getting thin(it was a lease maintained truck but I should have spotted it). I was able to back it off and flip it back into position. Next stop was truck repair shop down the street for linings. So far we have had good luck with self adjusters as long as they are greased regularly.Air tanks should be drained regularly as even with airdryer they still will get some moisture,the drains with pull cords make it easy to pop them when you are doing your walk around or fueling. Wetwilly glad no one was injured in incidents you describe. ABS, self adjusting slacks or the new to heavy trucks disc brakes do not eliminate the need for proper maintinence. To me air brakes are easier to work on and maintain.

In California, heavies ( especially fleets ) are inspected every 90 days. That's an inspection of all of the critical components. Brakes, steering, tires and rims, leaks, lights, etc. There is no excuse for letting brakes go thin or below specs. If you do think it's okay, let's apply that to air brake equipped school buses. Yeah, I'd prefer the 90 day inspection. Or, how about this, your driving down the road with the wife and kids. You are at a stop and you look in your rear view mirror and see a heavy coming up behind you. I'd feel more comfortable if the brakes on that truck were inspected regularly!

Pre trip inspections by the driver are mandated by the Federal Highway Safety Adm. Possibly he should consider a course like this before he ever steps into a vehicle with air brakes.

http://www.nhi.fhwa.dot.gov/trainin...y=web%20based&num=&loc=&=sta

Texas requires an annual inspection, which I am licensed to do. States can make criteria more stringent than the USOT annual inspection, but not less. We haul bulk commodities grossing 84,000 on 5 axles in the Texas Hill Country. Our brakes are inspected annually, at our 15,000 oil and grease job intervals, but most importantly during the pre trip inspection. And furthermore, drivers are required to turn in a written post trip inspection. Part 396 of the Texas statutes clearly describe the need for a pre trip inspection report. It is the driver's first responsibility to check the brakes.

http://www.txdps.state.tx.us/internetforms/Forms/MCS-9.pdf

If he doesn't know how or doesn't want to do it, he needs to stay out of a vehicle with air brakes. They are not toys.