Manual drum to disc 3/4 ton - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72c20customcamper · 01-04-2019, 12:42 PM

Truck im looking at has manual drum brakes. How much of a hassle and expense is it to convert to power disc. It's a 70 by the way.

Reason being my wife will be driving it from time to time. Also would want to add power steering at some time

**Steeveedee** · 01-04-2019, 02:56 PM

Easiest swap is to add a booster to it. I upgraded to disc because they stop better, especially in the rain. You'll get differences of opinion, but that is mine. Given where you live, disc brakes would be a good option. It is a lot of work if you buy a kit to convert over.

**jocko** · 01-05-2019, 01:15 AM

Kits can be purchased, but I think the best approach is to find a donor 71+ C20 setup. 73-87 may even be preferred to 71-72. At the very least, less expensive, more common/available. Makes finding/buying replacement parts much simpler and provides factory power disk performance. Price depends on how good a deal you get at the junkyard on the parts. Can do a crossmember swap or every thing but the crossmember, I believe, but some considerations regarding lower control arms. I haven't done this swap, so can't really tell you if it's painful - but if I WERE going to so this swap, that would be how I'd plan to do it.

A couple of threads for additional info:
http://67-72chevytrucks.com/vboard/s...d.php?t=763609
http://67-72chevytrucks.com/vboard/s...d.php?t=536728

4carbcorvair · 01-05-2019, 11:11 PM

I have power drum on my 68 K20 wrecker. I've towed a few times with it, small car trailer with a Toyota pickup on it and a tow dolly with a 97 Chevy pickup. Had no issues stopping. The brakes are clean, adjusted properly with new wheel cylinders and master.

Myoldtruck · 01-06-2019, 01:28 AM

70 with 4 wheel drums. I added a brake booster and it made a huge difference. Install new parts all the way around, new rubber hoses. Buy the best shoes you can, clean and adjust everything. I have no problems, stops like any other car I drive. i tow a 23ft airstream trailer, that has its own electric brakes, I have no problems.

Real question is what kind of driver is your wife. Mine scares the hell out of me in her minicooper, drives to fast, tailgates, and slams on brakes at last minute. Not the type of person to drive old cars with even the best brakes.

Droff · 01-07-2019, 10:27 AM

I converted my '68 from drum to disc. I found a donor '86 3/4 ton for the parts - control arms, booster, mc, prop valve, rotors, calipers. They were in worse shape than I expected or verified when I purchased so I pretty much had to buy replacement parts for my replacement parts. New ball joints, rotors, calipers, booster and mc. Not a good plan on my part so it didn't work out to a cheaper, better alternative than buying a kit.
If there is a next time, I'd just buy a conversion kit and not worry about a donor. Replacement parts for the kits shouldn't be any harder to find than for a donor, as long as you pick up a kit from a well known vendor.

OldBlue70C10 · 01-07-2019, 01:37 PM

[QUOTE=Myoldtruck;8437610]70 with 4 wheel drums. I added a brake booster and it made a huge difference. Install new parts all the way around, new rubber hoses. Buy the best shoes you can, clean and adjust everything. I have no problems, stops like any other car I drive. i tow a 23ft airstream trailer, that has its own electric brakes, I have no problems.

I think this is the route I may go. What brake booster did you use? And where did you tap into for vacuum, the intake manifold?

kenr74 · 01-07-2019, 01:50 PM

I swapped a 72 front end into my 69 C20. Very straight forward and easy to do. I spent more time bending a new brake line than the rest of the swap. Would have been easier to just buy a new prebent line.

72c20customcamper · 01-07-2019, 01:53 PM

Thanks for the input but I didnt by the truck. Just to much wrong with it

Myoldtruck · 01-07-2019, 10:25 PM

I bought the complete booster and m/c from advance auto online. I bought the mounting bracket for the fireway on ebay new. Tied in vacume from rear of the intake manifold. Your going to have to buy or bend new lines from the M/c to the proportional valve ( its a tee block really without discs). Your 3/4ton has larger drums and shoes than a 1/2ton, your going to have plenty of braking power.

I used napa premium brake shoes. Converting to disc brakes is not high on priority list right now.

01-04-2019, 12:42 PM	#1
72c20customcamper Registered User Join Date: Jul 2018 Location: Catskill Mountains,NY Posts: 8,728	Manual drum to disc 3/4 ton Truck im looking at has manual drum brakes. How much of a hassle and expense is it to convert to power disc. It's a 70 by the way. Reason being my wife will be driving it from time to time. Also would want to add power steering at some time __________________ Mark 72 c20 custom camper Husky edition, 66 SS396 Chevelle 1964 Hawk, 63 Avanti,62 lark 1969 AMX , 1968 c20 stepside ,85 K20 1977 Suburban sold 68 anniversary.

01-04-2019, 02:56 PM	#2
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,708	Re: Manual drum to disc 3/4 ton Easiest swap is to add a booster to it. I upgraded to disc because they stop better, especially in the rain. You'll get differences of opinion, but that is mine. Given where you live, disc brakes would be a good option. It is a lot of work if you buy a kit to convert over. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

01-05-2019, 01:15 AM	#3
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,975	Re: Manual drum to disc 3/4 ton Kits can be purchased, but I think the best approach is to find a donor 71+ C20 setup. 73-87 may even be preferred to 71-72. At the very least, less expensive, more common/available. Makes finding/buying replacement parts much simpler and provides factory power disk performance. Price depends on how good a deal you get at the junkyard on the parts. Can do a crossmember swap or every thing but the crossmember, I believe, but some considerations regarding lower control arms. I haven't done this swap, so can't really tell you if it's painful - but if I WERE going to so this swap, that would be how I'd plan to do it. A couple of threads for additional info: http://67-72chevytrucks.com/vboard/s...d.php?t=763609 http://67-72chevytrucks.com/vboard/s...d.php?t=536728

01-05-2019, 11:11 PM	#4
4carbcorvair Registered User Join Date: Feb 2018 Location: Gorham, ME Posts: 96	Re: Manual drum to disc 3/4 ton I have power drum on my 68 K20 wrecker. I've towed a few times with it, small car trailer with a Toyota pickup on it and a tow dolly with a 97 Chevy pickup. Had no issues stopping. The brakes are clean, adjusted properly with new wheel cylinders and master. __________________ 68 K20 Custom Camper/CST Wrecker. 97 GMC K1500 short bed reg cab.

01-06-2019, 01:28 AM	#5
Myoldtruck Registered User Join Date: Sep 2015 Location: Mohnton pa. Posts: 208	Re: Manual drum to disc 3/4 ton 70 with 4 wheel drums. I added a brake booster and it made a huge difference. Install new parts all the way around, new rubber hoses. Buy the best shoes you can, clean and adjust everything. I have no problems, stops like any other car I drive. i tow a 23ft airstream trailer, that has its own electric brakes, I have no problems. Real question is what kind of driver is your wife. Mine scares the hell out of me in her minicooper, drives to fast, tailgates, and slams on brakes at last minute. Not the type of person to drive old cars with even the best brakes.

01-07-2019, 10:27 AM	#6
Droff Registered User Join Date: Dec 2016 Location: OKC Posts: 130	Re: Manual drum to disc 3/4 ton I converted my '68 from drum to disc. I found a donor '86 3/4 ton for the parts - control arms, booster, mc, prop valve, rotors, calipers. They were in worse shape than I expected or verified when I purchased so I pretty much had to buy replacement parts for my replacement parts. New ball joints, rotors, calipers, booster and mc. Not a good plan on my part so it didn't work out to a cheaper, better alternative than buying a kit. If there is a next time, I'd just buy a conversion kit and not worry about a donor. Replacement parts for the kits shouldn't be any harder to find than for a donor, as long as you pick up a kit from a well known vendor. __________________ '68 GMC 3/4 Ton 350, 700R4

01-07-2019, 01:37 PM	#7
OldBlue70C10 Registered User Join Date: Jul 2018 Location: Ozark, AL Posts: 43	Re: Manual drum to disc 3/4 ton [QUOTE=Myoldtruck;8437610]70 with 4 wheel drums. I added a brake booster and it made a huge difference. Install new parts all the way around, new rubber hoses. Buy the best shoes you can, clean and adjust everything. I have no problems, stops like any other car I drive. i tow a 23ft airstream trailer, that has its own electric brakes, I have no problems. I think this is the route I may go. What brake booster did you use? And where did you tap into for vacuum, the intake manifold?

01-07-2019, 01:50 PM	#8
kenr74 Registered User Join Date: Apr 2018 Location: NW, Oregon Posts: 51	Re: Manual drum to disc 3/4 ton I swapped a 72 front end into my 69 C20. Very straight forward and easy to do. I spent more time bending a new brake line than the rest of the swap. Would have been easier to just buy a new prebent line.

01-07-2019, 01:53 PM	#9
72c20customcamper Registered User Join Date: Jul 2018 Location: Catskill Mountains,NY Posts: 8,728	Re: Manual drum to disc 3/4 ton Thanks for the input but I didnt by the truck. Just to much wrong with it __________________ Mark 72 c20 custom camper Husky edition, 66 SS396 Chevelle 1964 Hawk, 63 Avanti,62 lark 1969 AMX , 1968 c20 stepside ,85 K20 1977 Suburban sold 68 anniversary.

01-07-2019, 10:25 PM	#10
Myoldtruck Registered User Join Date: Sep 2015 Location: Mohnton pa. Posts: 208	Re: Manual drum to disc 3/4 ton I bought the complete booster and m/c from advance auto online. I bought the mounting bracket for the fireway on ebay new. Tied in vacume from rear of the intake manifold. Your going to have to buy or bend new lines from the M/c to the proportional valve ( its a tee block really without discs). Your 3/4ton has larger drums and shoes than a 1/2ton, your going to have plenty of braking power. I used napa premium brake shoes. Converting to disc brakes is not high on priority list right now.



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