Help with Drum Brakes

[Jaxson]

I have a 1984 GMC Sierra K2500. It used to be the diesel before the previous owner put a gas SBC 350 in. It has a 14 bolt rear end. I bought the truck with no parking brake cables hooked up. I ordered in new parking brake cables from LMC truck only to find that my truck has the older style parking brake, the one where it bolts in. I have new cables with the push-in design. I can't find the two bolt cables anywhere online. So, I have decided to try and buy new backing plates with the newer style parking brake. But I can't find them anywhere. I am also unsure what size of brake drums I have. My shoes are 2 3/4" wide which LMC says I have the 11-5/32" brakes. Does that mean the brake drum is 11-5/32 or something else?
My current backing plate is 12 1/4" in diameter with the axle hole being 3 3/4" in diameter. The outside diameter of my drums is about 14 inches.

So overall my question is if anyone knows what size my drums are and if you have a part number for the correct backing plate. Or part number for the correct parking cables.

Thanks in advance, this is my first time posting on a forum.

 

[Juggernaut]

That 2 bolt plate on mine is just a cover or guard. My cables are the push in design that snaps into the backing plate, and the rear end is a 75. Are the 2 bolt covers missing and you can see it bolts in? I've never seen a bolt in design

 

[Jaxson]

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I don't necessarily need to find the part that bolts into the plate. I just bought the truck and later discovered it was missing cable parts. So another solution would be helping me find what I am missing to connect all 3 of those ends. As it seems right now is that the cables aren't long enough to reach each other. I just can't find any good information on the parts and routing that the older parking cables had.

 

[Jaxson]

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On the driver side there is a bracket like this. Not on the right side though and the right cable isn't long enough to go into the top hole of that bracket.

 

[Rusty Nail]

@pduffyd maybe could help?

Great pixs.
The driver side operates the passenger side - they are certainly different to some extent.

 

[RecklessWOT]

Little nitpicky **** from trucks that may or may not have been molested by previous owners with parts from lord only knows what year truck can be frustrating to say the least. I for one can't give you any info on this because any square I've ever had was automatic so I never even knew if the parking brake worked or not, can't say I've even tried it once (no need for it unless you want to leave your standard shift truck running in neutral to warm it up or something, otherwise park works just fine lol). Looks frustrating, but I can't imagine the brake cable would be so different from one year to the next. You may be missing a part or just not looking at it the right way, easy to do with this old stuff. There are a lot of guys here that know like everything there is to know about everything, just because us guys so far can't spot the issue from a mile away does not mean the next guy won't..
Good luck, I hope to see you figure it out soon

 

[Blue Ox]

My guess would be that somebody swapped a rear somewhere in your truck's past. 14 bolt semi-floaters aren't the best thing GM ever came up with. So you're probably going to have to look at older (probably pre '80) parts books to find cables. When they refer to drum size they're talking about inside diameter. Hope that helps.

 

[Juggernaut]

Is that a semi floating 14 bolt rear? The cables sure look like my 14 bolt full. Do you have hubs sticking out of the wheels with bolts in them? If it is a full floater, I would say you will not be able to use those existing cables. In the picture of the drivers side bracket you can see there is a hole above the hole you have the cable running through. That hole is for the passengers side cable. On your 84+ the passengers cable is a much longer cable that runs along the axle, through the drivers side mount, then both cables attach to the parking brake cable through a single bracket. All these parts are available from LMC. If its a semi floater I can't help, I know nothing about them

 

[pduffyd]

Hi Jaxson.

I rebuilt my 14 bolt ff rear on my 76 C20.
I will have to measure the dia' of the back plate. But yours look different to mine, I have 13 x 2.5 in brakes.

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[pduffyd]

https://www.lmctruck.com/1973-87-chevy-gmc/cc-1973-83-parking-brake-cables-2-wd

This is my park brake setup, note item 4, its the gasket between the 2 bolt cable clamp and the drum. Its needed to keep water out of the rear brakes.

 

[Jaxson]

Thanks for the help and input to all. So I did come to the conclusion that a previous owner had swapped in a 14 bolt semi floater into the truck at one point. It had the 11 inch drums with the older style parking brake. However my truck frame is set up to take the newer style parking brake cables. So I guess the previous owner decided to just not run a parking brake, which I am now stuck with. And there are no new backing plates on the market for the 11in drums, just the 13in ones. I just decided to throw everything back together and just go without a parking brake for now. In the future I will put in a 14 bolt full float with 13 inch brakes.

 

[pduffyd]

Always good to have a plan.
The most common seems to be 4.10 ratio.
All depends what you want as the axle ratio. 3.21, 3.42, 3.73, 4.10, etc.
Happy hunting.

 

[Rusty Nail]

Thx Puffy

 

[Scott Delaney]

Rather than start a new thread I thought I'd add to this one.

I recently had need to replace the front brake pads on my 1983 Chevrolet C20, 6.2 Diesel. I have a semi-floating 14 bolt rear end with 9.5 inch ring gear (3.42)

Of course, you need to know whether you have 11 or 13 inch rear drums when you buy front pads, so I measured. The outside diameter of my drums is 13 inches, so I bought the appropriate pads and installed them without issue. They also lined up the same with the old pads. They're working perfectly.

Today I opened up my rear brakes to put an eyeball on them. They're looking a little worse for wear so I'm going to change them.

I measured the outside diameter of drum again - 13 inches. Then I measured the shoe, which is 2.75 inches.

The previous owner was the original owner and did not swap out the rear end.

So . . . what the heck?

 

[Blue Ox]

It's the inside diameter. The wrong front pads will fit the calipers.