Rear disc conversion

gerhed · Jul 13, 2024

So I have a 1983 K20 with the semi float rear axle. I want to convert it to a disc set up and was wondering if the same setup that works on a full floater will work on a semi float. The adapter plates are about $50 on Amazon, and I've watched some videos of people using the front rotors and calipers from same year, and it looks like that once the adapter plate is on, everything else but the line fabrication is a bolt on. What I can't seem to find is a video of somebody doing this on a semi float rear diff.

Anybody know about this can maybe shine a little light my way?

Doppleganger · Jul 13, 2024

What will you use for a parking brake?

gerhed · Jul 13, 2024

Doppleganger said:
What will you use for a parking brake?

line lock kit

SquareRoot · Jul 13, 2024

gerhed said:
line lock kit

Nooooo. Line locks bleed off.

Old Guy Bill · Jul 13, 2024

I looked into it when I began my rebuild on my K20…
In my opinion that conversion is a lot of money and effort for very little return

gerhed · Jul 13, 2024

SquareRoot said:
Nooooo. Line locks bleed off.

Well, ok then.

Grit dog · Jul 13, 2024

If you’re up against rebuilding and replacing everything on the rear brakes including drums, then maybe it’s the right time to convert. Similar cost magnitude.
Or if you plan on daily driving it through a couple sets of brake pads like you’re gonna pile on 150k miles in the next 5 years. I’d think about it.
But if all u need is shoes wheel Cylinders and maybe a hardware kit, drums are hard to beat and if they are in new condition they will last a long time and stop very well.
JMO. Sorry I didn’t answer your question. I don’t know that answer.

gerhed · Jul 13, 2024

Grit dog said:
If you’re up against rebuilding and replacing everything on the rear brakes including drums, then maybe it’s the right time to convert. Similar cost magnitude.
Or if you plan on daily driving it through a couple sets of brake pads like you’re gonna pile on 150k miles in the next 5 years. I’d think about it.
But if all u need is shoes wheel Cylinders and maybe a hardware kit, drums are hard to beat and if they are in new condition they will last a long time and stop very well.
JMO. Sorry I didn’t answer your question. I don’t know that answer.

Nah, you answered just fine. I only put 4-5,000 miles a year on my work truck, which is what this will be, so, I think I'll just keep the drums.

Very convincing argument, thanks.

WFO · Jul 14, 2024

gerhed said:
Nah, you answered just fine. I only put 4-5,000 miles a year on my work truck, which is what this will be, so, I think I'll just keep the drums.

Very convincing argument, thanks.

Good plan, especially since the front brakes do most of the work.

JBswth · Jul 21, 2024

gerhed said:
So I have a 1983 K20 with the semi float rear axle. I want to convert it to a disc set up and was wondering if the same setup that works on a full floater will work on a semi float. The adapter plates are about $50 on Amazon, and I've watched some videos of people using the front rotors and calipers from same year, and it looks like that once the adapter plate is on, everything else but the line fabrication is a bolt on. What I can't seem to find is a video of somebody doing this on a semi float rear diff.

Anybody know about this can maybe shine a little light my way?

I would, instead, switch to a 14 bolt Full Floating rear end with 13 inch brakes. More bang for the buck.

J. B.

Bennyt · Jul 22, 2024

JBswth said:
I would, instead, switch to a 14 bolt Full Floating rear end with 13 inch brakes. More bang for the buck.

J. B.

This is what I'd do. Stronger axle, bigger drums.

Rickf · Jul 22, 2024

Doppleganger said:
What will you use for a parking brake?

The kits I've seen use mid 80's Eldorado/Toranado front calipers.

Bennyt · Jul 22, 2024

Rickf said:
The kits I've seen use mid 80's Eldorado/Toranado front calipers.

I've done 2-3 14BFF rear disc conversions and those calipers don't hold very well. I think the pedal/ lever needs more travel. I used a ratcheting lever on one and it was better. If I ever use Eldo calipers again, which I won't, I think the trick would be to use an e-stopp to pull it up tight.

Rear disc conversions aren't really worth it unless you are spending big money and racing. Rear drums work well and are reliable. If 30-40% of your braking occurs in the rear and a disc conversion improves it by 10-20%, you see less than a 10% improvement overall. Put the same money into larger drums in rear and better front calipers up front and you'll be way ahead

Craig Nedrow · Jul 22, 2024

FYI the 14 bolt has several different drum sizes 11, 13, and at least two width sizes, 2.5 and 3" I think.....Bigger is better

Grit dog · Jul 22, 2024

Craig Nedrow said:
FYI the 14 bolt has several different drum sizes 11, 13, and at least two width sizes, 2.5 and 3" I think.....Bigger is better

And a 14 sf may already have the big brakes.

Rear disc conversion

gerhed

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