The GMC CCKW

Hello...

Several of my rear brake adjuster bolts (Banjo axle) are pretty sloppy with respect to their fit on the pinion (I think that's what it is called - the bumpy disk that engages the wheel cyl caps). On some, I can turn the bolt 40 or 50 degrees before the pinion starts to turn. Others are tight and have no slip at all. Aside from making it more difficult to adjust the brakes, I am concerned that the pinion may pop off and fall into the drum.

Is there a good way to tighten these up? The parts book shows them, but are they really serviceable? I did not see a replacement procedure in any of the manuals.

It looks like the end of the adjuster bolt is spun over on top of the pinion? I'm thinking maybe pull the backing plates off and TIG weld the bolt to the pinion ?

Any help or suggestions would be greatly appreciated...

Best Regards.

As I mentioned, several of the adjuster pinions on my rear brakes were either very loose or stripped out, making it impossible to adjust the rear brakes - as the pinion would just remain stationary as the adjuster shaft was turned.

https://drive.google.com/file/d/18ewaEQ ... sp=sharing

I buddy of mine has a MIG welder, so I decided to attempt the welding repair method. This approach presented two concerns:

1) That I could remember how to weld (its been quite awhile since I have last tried it).

2) That I might over-penetrate the weld, and inadvertently weld the pinion/shaft assembly to the backing plate.

So, with #2 in mind, the first order of business was to try to isolate the pinion from the backing plate. For this I took a scrap piece of steel, drilled a hole in it, and along with a bolt and some washers used it as a "compressor" to push on the shaft ends, lifting the pinions away from the backing plate.

https://drive.google.com/file/d/1PEVIw4 ... sp=sharing

Next I took a copper washer, sliced a slot in it, and slid it behind the pinion. The idea here is that since the weld will not stick to the copper, the washer will protect the pinion/backing plate interface from the weld. (Note, some might suggest that a pre-1982 copper penny pounded flat with a hammer, drilled and trimmed with a tin snips would work well for this - however everyone knows that it is illegal to deface US currency...)

https://drive.google.com/file/d/1UYKJ6p ... sp=sharing

After the washer was slid into place, the compressor bar was removed. The ground clamp of the welder was connected directly to the pinion shaft and the weld was made. It was then ground smooth using a Dremel to prevent interference with the wheel cylinder caps. The springs were re-compressed, the area behind the pinions was cleaned, then lubed with brake grease, and the compressor was removed.

https://drive.google.com/file/d/1nwd631 ... sp=sharing

So far it seems to work well. At least I can adjust my brakes again.

Best Regards...

On the rears, I take the 5/8 wrench and go back and forth with the adjusters every 6 months or so to keep things free.

On the rears, I take the 5/8 wrench and go back and forth with the adjusters every 6 months or so to keep things free.

I think that this would be a very good idea, especially if the truck has been sitting for awhile.

Has anyone had any experience applying some type of surface treatment to the wheel cylinders and/or caps? I was thinking maybe powder coat, or perhaps trying to get the caps nickel plated maybe - but I am concerned about the clearances.

I plan on reassembling the wheel cylinders using a silicone based high temp brake grease to help keep out the moisture. But besides that, those surfaces are relatively unprotected. Sometimes I think you can almost watch them rust....

Best Regards...

p.s. BTW, what do the DUKW guys do? I can't imagine submerging those cylinders in salt water. Or do the DUKWs use a different design?

I put some high temp grease under the cap (not too much) to keep the water out and prevent moisture from rusting the bore. I put anti-seize compound on the adjusting screw threads and work it in thoroughly. It works so well, it is now SOP on all my GMCs and Chevys.

PS: ALWAYS carry a brake shoe return spring with you. If one breaks, it will stop you dead!

http://imageshack.us/photo/my-images/15/jioo.jpg/
This mine extra cylinder I welded the teeth.

Hi Fernando,

Just curious... Were the teeth broken or worn ?

Best Regards...

Broken in many parts.

http://imageshack.us/photo/my-images/833/rgm4.jpg/
mudflap,can you see?

http://imageshack.us/photo/my-images/706/rcdw.jpg/
That is better.

Fernando,

Whoa! That is serious! What do you think caused it to break like that ?

BTW, good job on the welding!

When I bought my CCKW the cylinders were all clogged in the wheels.Who did for me the welds was a boy that is a good artificer.Send pics of your truck.My e-mail is Regards.

BTW: If you want to "flush" you system, do it backwards. Force fluid into the wheel cylinders thru the bleeder and open the other end (booster) otherwise, all the gunk (technical term) and rust will be forced into your wheel cylinder and it will probably be too heavy to be forced out through the bleeder. Sitting on the bottom, it will cause your rubber cup to fail eventually.

Has anyone had any experience applying some type of surface treatment to the wheel cylinders and/or caps? I was thinking maybe powder coat, or perhaps trying to get the caps nickel plated maybe

FYI... Finally found a local plating company that plated my brake adjuster caps with zinc dichromate.

https://drive.google.com/file/d/17Q5UwO ... sp=sharing

Also coated the inner surfaces and threads with a high temp, silicone based brake grease (won't hurt rubber brake parts).

https://drive.google.com/file/d/1AURHyU ... sp=sharing

https://drive.google.com/file/d/1eBDbS0 ... sp=sharing

We'll see how this works to help keep those adjusters adjustable.

Best Regards...

Nice job.Congratulations.

Mudflap,can you send me how did you do these parts?I would like to do the same project.

Hi Fernando,

It was actually pretty easy. The toughest part was just trying to find a local plating company that was willing to do such a small job. Most places are setup for large scale production and are not interested in doing "custom" work. I finally asked around at a local car show, and the classic car guys put me in touch with a place that would take this job on.

To start, I cleaned the caps thoroughly. I don't have access to have any type of media blasting equipment, so I just used a wire wheel to knock the rust off of the inner and outer surfaces. The guy at the plating company recommended the yellow finish as being the most durable of the zinc chromate finishes they offered. They did a little additional cleaning, and then plated the parts. I picked them up a few days later.

The grease shown in the pics is Permatex 24115 disc brake caliper lubricant.

http://www.permatex.com/component/docum ... automotive

I picked this grease because of its high temperature rating, its good lubrication properties (contains molybdenum disulfide), and - most importantly - its compatibility with rubber brake components since it is silicone based.

My concern with petroleum based lubricants for this application is their potential to damage the rubber seals in the wheel cylinders if the lubricant ever comes in contact with them.

Best Regards..

The importance of correct brake setup, adjust maintenance is shown on the skid marks in my barn:

I have just developed a problem with the rear-rear duals on one side. Coming into the barn the other day slowly, it locked up and skidded on the smooth floor. I heard it and noticed that it did and was slow to release after. Upon inspection last night. The front-rear duals n the other side skidded too, but not as much. Because the axles are powered together by the xfer case, you have very heavy mechanical computer. When something happens to one brake like this, it affects something on the other axle. This is how you can get into a BAD SKID!!!

I will investigate tomorrow and probably clean and rebuild all four stations and will try the grease mentioned earlier in this string instead of my hi-temp chassis grease; Thanks

Complete new job. I will replace the shoes and wheel cylinder. I am going t use the aforementioned disc brake lube as opposed to my red grease ( I thought I never had used the red grease on these). Being red grease, it must have been done over 10 years ago! That is a long time for a CCKW. When I do the middle axle, I will use my blue Amine grease for comparison. The disc grease is thicker and not as slick. We shall see.

On a different note, I stole the 2 rear cylinders from my Chev Panel truck in progress. The brass lines, sealed cylinders has the metal pistons starting to RUST!

My ideal cylinder is as follows:

SS lined
Brass pistons
plated adjusting cups (something that won't rust)
Turn the ends of the cylinder down where the cup rides and install a SS ring for the cup to ride on

Dr. Deuce,

So, what do you think was the root cause of the brakes hanging up? Were the piston cups swollen? Or were the pistons sticking to the cylinder bore? Either way, 10 years definitely seems like pretty good service for this type of design.

I went the SS sleeved cylinder route as well. There was a lot of rust in the hydraulic system when I took it apart.



The left side shoes on the trailing axle had been hanging up big time...

I'm working on bending up brake lines now - also SS. Most of the ones that are on the truck appear to have been replaced, although the insides look kinda corroded. Plus, the previous installation could have been better, as there are almost as many kinks as there are bends.

Your idea for adding a SS ring on the end of the wheel cylinder is intriguing... How would you secure it to the wheel cylinder?

Too bad no one with an NC machine and some extra time on their hands hasn't started cranking out SS wheel cylinders and caps. Would probably be cost prohibitive, but would sure solve a lot of problems...

Best Regards...