'71 C-20 Front Disc Brakes to '69 C-20

[Sinister]

What all is involved with putting spindles and disc brakes from a '71 C-20 onto my '69 C-20?

[Sinister]

Bump

[ERASER5]

I think that all the 3/4 tons use the big lower ball joint. That being the case, use your '69 A-arms and the rest should be a direct parts swap up to the front brake lines. You may need to relocate the steel lines to fit the rubber hose mounting location. To avoid any steering issues, I would use the '71 drag link and tie rods. Of course you will need the disc/drum M/C and prop valve.

The key is the lower ball joint.

Are you adding a vacuum booster as well? If so, grab EVERY part all the way to the pedal.

[Sinister]

Thanks for the reply. I'll have to check and see if '69 and '71 ball joints are the same. I'm pretty sure he has the prop valve and master cylinder. Will these bolt to the booster I have already? Why don't you think the drag link and tie rods from the '69 will work?

[Sinister]

O.K. a couple of more questions. The '69 tierods won't work. What is the center piece called that the tierods attach to? Apparently '71'-'72 boosters are different then '69 boosters so basically, would the '71 MC possibly work with the '69 booster? Would it even bolt up?

[ERASER5]

The drag link is the center piece. The tie rod tapers are different, that is the problem. The M/C should work but there may be a difference in the Delco and Bendix brands. A Delco booster works with a Delco M/C and a Bendix boost with a Bendix M/C. That is the only difference that I am aware of.

But I have been wrong before...

[leddzepp]

You will need a different master cylinder as you have drum/drum with the 69 brakes. You need a disk/drum master cylinder. I was not aware of the power boosters being different throughout our years, other than being either Delco or Bendix...but I am not sure. When I replaced the master cylinder in my 72 C/20, there was only one part listed for power disc brakes, and did not specify whether it was Delco or Bendix.

Sin- I walked by your truck several times today at Brothers, but you were never there! I ran into a couple of guys from the meet a few weeks ago.

[Sinister]

Hey Scott. I looked for your truck but didn't see it. Which one did you drive? I know I'll need a drum/disc MC, just wondering if a '71 MC will bolt up and work with the '69 booster.

[leddzepp]

Sin- I decided at the last minute to take my blue/white truck instead. I was in the middle of doing something on the 3/4 ton and did not feel like putting it back together

I just looked at my Classic Trucks parts catalog, and they do list two different power boosters (67-70) and (71-72) for 3/4 ton trucks. They are both listed as Bendix type. So you will need the power booster from the 71, and I'd say you would also need the proportioning valve from the 71. As Eraser 5 stated, get EVERYTHING. I have read on here that the difference between the power boosters (Bendix or Delco) is the bolt pattern on the back that mounts it to the brackets. So get the brackets if you can.

[Sinister]

Now I'm concerned about the a-arms. LMC shows a part number for '71-'72 a-arms which probaly means the earlier ones are different. I might have to wait on this swap, the guy with the parts is very proud of them.

[ERASER5]

If you do need the 71+ A-arms, you only need the lower arms. Two U-bolts (each arm) and your done. Of course your best bet is to get ALL-- the whole enchilada-- the brake and suspension parts. This will help you to have everything laid out, cleaned, painted and ready for install. But that is just me..

[ERASER5]

If your bud doesn't want to sell, then bypass him. Any 73 to 87 C20 will give you the lower parts you need. You can just buy the entire cradle with suspension and brakes attached.(I paid $125 for an entire frame front to shock mounts. I got about $75 back from the left over scrap metal) Then you can swap parts or swap the whole cradle. Which way depends on how much cleaning and painting you like.

I do not know if the 73+ booster fits our brackets or not. The prop valve should be adequate. The M/C should be close, but again I am not sure. However, a new '71-'72 M/C and booster are still made. I would buy the M/C first to check for fit. If the fit is not right, then I would buy the matching booster. You did say you already had power brakes right?

[spyder4560]

Don't mean to hijack your thread,but I went through the same deal a while back.Here is my story.69 GMC 3/4 ton(same parts as Chevy)2 wheel drive.Used a 72 lower ball joint as it's the same diameter as the hole in your 69 LCA,and may as well put the top ball joint on while you are in there.Use the 72 tierod end(outer)and make sure you have the 6" adjuster sleeve.Myself,I changed the brake hose to 73 for the extra length and lower cost.71 or 72 M/C and booster and prop.valve,couple of adapters for the lines at the prop.valve and I was good to go.BTW,I have some 72 spindles,rotors,and calipers if you need a part or two,just PM me.

[Sinister]

Originally Posted by spyder4560

Don't mean to hijack your thread,but I went through the same deal a while back.Here is my story.69 GMC 3/4 ton(same parts as Chevy)2 wheel drive.Used a 72 lower ball joint as it's the same diameter as the hole in your 69 LCA,and may as well put the top ball joint on while you are in there.Use the 72 tierod end(outer)and make sure you have the 6" adjuster sleeve.Myself,I changed the brake hose to 73 for the extra length and lower cost.71 or 72 M/C and booster and prop.valve,couple of adapters for the lines at the prop.valve and I was good to go.BTW,I have some 72 spindles,rotors,and calipers if you need a part or two,just PM me.

Thanks for the informative post. So the '72 tierod ends bolt up? Hmmm, '72 adjuster sleeve? '73 brake hose for a 3/4 ton?
Sounds good. I may PM you about those parts.

[Sinister]

Spyder, do you have any pics? I'd like to see the master cylinder/ prop valve especially.