C20 Disc brake questions

[rangernsk]

I just got a 72 C20, I want to put the disc brakes on my 70 C20, what do I need off the 72. Do I need the A arms, power break booster, prop. valve and of course the spindles, rotors and calipers? My 70 already has power breaks, are the boosters the same on disc and non-disc setups? Are the brake lines different? Just want to make sure I get everything I need off the part truck before I get rid of the rest.

[rangernsk]

ttt

[cableguy0]

the easiest thing to do is probably just take the whole suspension cardle out from under the 72 and bolt it under the 70. then u need to swap the booster master cylinder adn proportioning valve too. also make sure the steel lines all match and are goint o the same place ont eh 70 as they were on the 72. i would say to swap out all of the hydraulic components like the master cylinder calipers rubbers hoses and maybe even the proportioning valve.

[Classic Heartbeat]

I recently did this swap into my 67 3/4 ton. I chose to do the entire crossmember and power break system. The drum brake system will stop the truck, but I feel it is dangerous because the two different types of brakes require two different pressures for them to work right. You have the parts, so use them... It is a lot safer that way and will only add a little time. Your frame is drilled for the different brake line clamps, so that isn't a problem. The crossmembers are different also. They are different in two places. 1.) The location for the mounts for the rubber brake lines. 2.) The forward hole in the side that has the bolt welded to it is slightly off also. (Easy fix with a file.) Anyway swapping the entire thing will eliminate any problems that will arrise in the future. Problems like what year do I need ball joints, tie rod ends, bearings, brake lines or any other host of things. If you swap the whole works then as far as the front end is concerned, it is 72! The other problem that the old crossmember presents is the location of the flexable rubber line. The 71-72 crossmember, it is located on the front and the 67-70 is on the rear. That creats pinching problems with the rubber line and may not cause an immediate hazzard, but surely will in the future as the lines pinch pretty bad when turning your wheels full one way or the other. WES www.ClassicHeartbeat.com

[Mike C]

I did this swap on my '70 GMC 2500. I took the spindles and control arms off the donor truck along with the prop valve and tie rod assemblies (innner and outer as well as sleeves.) I bought new steel lines for a '71 along with new rubber hoses. I cut the hose tabs from the frame of the donor truck, then after positioning new steel lines in my truck, I attached the rubber lines and located the cut-off tabs on the front of my frame where I tack welded them as they should be on a 71-72. I used the drum booster but disc master with the donor prop valve, but the drum booster is not as strong as the disc booster and my recommendation is to do the disc booster as well. Note that you will now have different size lug studs front and rear unless you swap rear axles or hubs as well.