Everybody needs them. At least some times.
I have had issues with the brakes, especially the front, since I bought my 48. At first, the left front was grabbing and pulling, hard. Took the drum off, cleaned and adjusted everything and it worked. Well, to some degree. The pull was lessened and seemed to be getting better with every drive.
The truck sat all summer as I redid the interior, converted to 12volts and rewired it.
Since finishing a couple weeks ago, I have had it out for pleasure runs and each time, the front brakes would grab and lock up. The tire squeal would scare everyone within 100 yards. I just learned to be very careful with the application and not put too much pressure, on the pedal, all at once.
Today, I start down the road and as I pulled into the first turn around, I apply light, but even pressure and everything was working as it should.
Then, all of a sudden, with a loud clunk, the brakes locked and the tires squealed. This while I am doing about 10mph. I had to back up a foot or two to unlock the brakes. It was like someone had thrown a switch and electrically locked them.
I know I will have to clean everything again and maybe even rebuild the wheel cylinders. Does anyone know what might be causing the sudden, violent grab? What should I be looking for, other than the obvious, like dry drums?

 

The only way I would drive one of these old truck is rebuild or replace each and every brake component. This rebuild would include all five cylinders, all three soft hoses, brake shoes, and all steel lines. All drums should be inspected and cleaned at minimum. The exception would be if I knew the brake system had recently been rebuilt by a trusted someone who was competent to do so. Then and only then would I attempt to troubleshoot an issue.
Anything with a soft rubber part should be a given as soft parts deteriorate. The steel lines should be replaced as they will and do rust internally and externally. Brake fluid is hygroscopic and the moisture can cause brake components to rust internally. The steel lines can collect dirt, moisture, and rust where they are clamped to the frame.
Remember, you have a single brake system and any failure can yield total loss of braking.

 

The man who rebuilt/restored the truck did the brakes at the same time. Aside from a minor weakness in his painting skills, I have found no reason to think it wasn't done right.
That said, the truck has been sitting a lot for the past 8 years. And there was that grabbing issue when I first bought it.
I don't disagree with you, Ray. I just didn't think a complete rebuild, of a complete rebuild would be necessary, (there is evidence of new steel lines and rubber hoses.).

 

It has been my experience that brake problems seem to fester when a vehicle is not used. Have you driven the truck while applying the brakes to heat the brakes, wear any surface rust from the drums and shoes? Have the brakes been bled, paying attention to clarity of the fluid. Eight years is a long time for a vehicle to sit.

 

Starting tomorrow, I will pull the drums and see what I have. I have had the truck for 18 months or so and the original issue was resolved in the beginning of ownership. After I get the drums off, I should know more about what has happened since then.
My real concern is the violence with which they locked up today. It was a loud pop, and they were locked tight. I have never experienced anything like that before.

 

I'm with Ray on the work needed. The last thing you want is a vehicle with sketchy brakes.

 

take a photo of setup, shoes reversed? I just did mine, but wont be testing for a while, as I hope to paint frame this weekend and start from there.

 

I think I may have mislead a few people at the outset. This truck has been re-done and used quite a bit. It has not just been setting. I drove it all last year, but have been working on it all summer. The issue has arisen since I started driving it again.
That said, it looks like I will be going to front disc. If I have to replace the drums and it appears I will, I might as well do the upgrade for a little bit more money.
Is anyone running the stock master cylinder with a proportioning valve setup?

 

The stock MC is not appropriate for a disc/drum setup. I wouldn't hit the panic button just yet, as said things can get out of whack from sitting. If the drums were OK last year, unlikely they suddenly need to be replaced.

 

Inspect the wheel cylinders before you go down the 'make it better' path.

 

Did all four wheels lock up?

 

I'm thinking a broken return spring or a broken pin that holds the shoes to the wall

 

That's what I'm thinking too. If only one wheel brake is locking up it might be improperly installed or broken parts. If all of the brakes lock up it would likely be in the master cylinder.

 

I had something similar happening in my 47 coupe .
The car would pull hard to the left when braking , you could feel the steering wheel pulling through your fingers .
Drove me crazy trying to work it out .
Turned out to be air trapped in the R/H front circuit .

 

Pic: C = F1/F100.