Any GMC truck experts on here?

coonie minnie · Aug 13, 2023

I've got a 1980 GMC topkick that has drum brakes in the front. The drums are badly worn, and I'm having a great deal of difficulty finding new ones. How difficult would it be to convert this to disc brakes? Any ideas?

Stephen Newell · Aug 13, 2023

Never done it before but need to. From what I can see the hardest part is the cost.

glennster · Aug 13, 2023

try these guys 119 dollars a drum.
poke here

NDIHC · Aug 13, 2023

Never did it on a medium truck, just old stuff. Had to remove the residual pressure valve from the master cylinder and install one just for the rear brakes. Front disc brakes just connected to the old drum lines with new hoses. Not sure how medium trucks were plumbed in the 80s though. Now I'm in the process of replacing the old single master cylinder with a new dual cylinder and booster with a proportioning valve set up for disc/ drum. So residual pressure valve will come back out.

Duner Wi · Aug 13, 2023

Napa, Advance Auto, Rock Auto all list the 2591R drums from $86.00 and up. Where you been looking?

Dingo3 · Aug 13, 2023

Shoes
Untitled URL Link

coonie minnie · Aug 13, 2023

I need drums with 5 bolt holes... I have the cast spiders that hold the wheels vs a 10 bolt wheel.

coonie minnie · Aug 13, 2023

Dumb question... if you replaced the drum style brake, what held the caliper for the disc style? Did yo need to replace the back plate that held the wheel cylinder for the drum brake??

NDIHC · Aug 13, 2023

I put in a whole new front suspension with new spindles that accepted disc brakes and installed the brackets for the calipers. This was on a 56 chevy pickup. I used Mustang II spindles and control arms with Monte Carlo rotors and calipers. I was mostly commenting on the hydraulic requirements of a drum/disc system vs. a 4 wheel drum system. I've never done the conversion on a medium duty truck. If I had to guess maybe spindles/knuckles from a truck with front discs along with the master cylinder/proportioning valve would be required. I know that drum systems use a residual pressure valve for front and rear where disc/drum use it only for the rear drums.

Duner Wi · Aug 13, 2023

Sorry ,I am stuck,
For used you could try Car-part.com.

rustred · Aug 13, 2023

u would need to replace the spindles. i am quite sure the parts are out there,.. try NAPA for one. or MOTION.

centash · Aug 14, 2023

Pick up a used front axle from a school bus, complete with wheels disc's etc...

Ben

INCase · Aug 14, 2023

I would think the dealer would be able to find the drums by looking at the VIN number????

caterpillar guy · Aug 14, 2023

So you have Dayton wheels instead of Budd wheels. Most drums are not necessarily vehicle specific. Take the old drum into most semi truck dealers, and they should be able to fix you up. Tell them it is on a Dayton wheel set up though, so they get the right bolt pattern for it. IF it is on 16 inch drums with 20 or 22.5 wheels should be pretty easy to find. The drums will bolt to the hub and so options are more open than if you had to get a drum for like your pickup. Most front brake shoes are 16x4 or just maybe a bit narrower for a medium duty truck like that. Most semi shoes fit the 16x4 pattern. Take the old shoes with you for it as there are a few options there. OR you could convert to hub piloted wheels. Then the drum would slide on the wheel studs so no wheel bearings to deal with in the future and tire size is easy to change by just bolting on a different wheel. We converted a dump trailer from Dayton wheels to hub piloted wheels saved some weight and made the brakes easier to service now. Also by going from Tall 24.5's to low pro 22.5's we lowered the trailer so it was easier to dump over with the combine.

JWinIndiana · Aug 14, 2023

This might help, a you tube video of the process.

https://www.youtube.com/watch?v=sebg51EheUo

Any GMC truck experts on here?

coonie minnie

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Stephen Newell

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glennster

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NDIHC

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Duner Wi

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Dingo3

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coonie minnie

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coonie minnie

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NDIHC

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Duner Wi

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rustred

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centash

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INCase

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caterpillar guy

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JWinIndiana

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