c20 drum to disk swap

[robby]

I may have a bead on a 69 C20 that is very original and nice with 68,000 miles original. Let's just say I got it, how hard would it be to change over to 71-71 front brakes to get the disk brakes? It has non power drums now. Would I need the control arms or just the spindles? Are the lug patterns the same in drum as disk?

[mikep684x4]

Do 71 and 72 c20's have the same disk setups?. I have a c20 eight lug disk brake front end complete that I'm trying to get rid of.Don't know if its worth the drive for you but the price is come get it!.I also have a set of six lug 15x8 truck ralleys,But those cost me a little to get.

[crazy longhorn]

the 71 & 72 are the same setup. To swap the 69 to disc, you will need.......centerlink, tierod assys(inners, outers,& sleeves), upper & lower balljoints, lower a arms(or grind steering stops to use the 69 lower arms), spindles , rotors, calipers, brake lines, hoses, master cyl, & prop valve.......I think that covers it! You dont need to replace the crossmember, but if you have one thats complete.......it might be just as easy to go that route. The lug pattern is the same, but im not sure about the stud sizing (you may have different sized lugnuts on one end of the truck).good luck....crazyL

[mikep684x4]

So if you unbolted the whole 71 crossmember,a-arms and all,It would work.Because I have the whole frame,perportioning valve and all.

[crazy longhorn]

Yup, the complete 71 crossmember will bolt in. the only differences in the crossmembers will be brackets for brake hoses....crazyL

[Longhorn Man]

71 and newer had 9/16 wheel studs, while the older ones with drums (70 and older) had 1/2 inch wheel studs.
You'll need 2 wheels to complete the swap.

[mikep684x4]

I got those too.

[robby]

So if the lugs are different you would need different wheels? Since I am only speculating and haven't driven the truck, how bad is the braking with drums on a 3/4 ton? Seems to me that towing anything would be a nightmare. What do you thing of just changing to power brakes? COuld you drill out the rearend for teh bigger lugs on the 69?

[Longhorn Man]

3/4 and one ons have huge drums...so big that you shouldn't even waste your time going to auto zone to get tehm turned. They stopped me as I walked in the door asking what the h*ll those things were off of.
When i redid the front brakes on the old Longhorn, they seemed to be pretty good. Brake fade was still an issue, but nothing nearly as bad as on the 1/2 ton trucks with those little sissy drums.

[robby]

Thanks, I guess if I score this truck I will leave it with drums and add power a booster. It is a low mile truck in really good shape.

[Mike C]

I HATE drum brakes. I bought my 70 3/4 ton truck and 3 days later bought a donor disc brake truck. Actually almost totaled mine on the way home with the donor on the trailer when a dumb a$$ in a suburban blew by me, cut in front of me, and slammed on their brakes to turn. Dodged that bullet and didn't drive the truck again until the brake swap was done. I don't have stock wheels, but aftermarket ones fit regardless of the lug size, and I believe stock should as well. Yes, you can swap the rear to same size as the front. If you get a donor truck, just swap hubs. Or take yours in to a machine shop and have old studs pressed out, holes redrilled, and new ones pressed in. I just bought matching lug nuts in a different size until I swap in my later rear axle.

As noted, you will need the spindles and everything attached to them, upper and lower balljoints, inner and outer tie rods and adjusting sleeves. Disc brake master cylinder and combination valve. You also will want to buy a new set of steel lines as the disc ones run in front of the crossmember and the drums behind.

Even my '64 Corvette is going to get a disc conversion. Originality be damned when it comes to performance.