69 C20 drums to discs from 74 C30-Is this doable?

[weim55]

I have a free ‘74 C30 donor that is a factory dual wheel truck. Can I purchase single wheel rotors and run everything else to put under my 69C 20? Is it best just to swap the entire crossmember with all the suspension components at the same time?

Steve weim55 Colorado

[Andy4639]

I'm having a whole 86 3500 put under my C-20 with disc brakes. The guy I hope will be done soon with it. I'm having him do the whole thing.

[Mike C]

Anything can be done. But MUCH easier to convert your C20 to C20 discs from a later truck rather than going C30. And parts should be cheaper.

[farmall]

I am not sure if the cross member will bolt up.

Will the spindles bolt up is a better question and can you run C20 hubs and rotors on C30 spindles.

Bearing and ball joint part numbers will tell you. You may need to swap steering parts as well.

Open up 3 rock auto pages and compare part numbers.

I am going to try 80s spindles on my 71 because the rotors are NLA.

I have the whole cross member dust cap to dust cap to play with.

[RichardJ]

I missed the DRW in the first post and assumed he is talking about a C30 SRW (single rear wheel).

I used a '76 C30 SRW as a donor for my '67 C20 (GMC 2500 actually).
I disassembled both and selected individual parts. The C30 had a bigger sway bar. The C30 big block springs were too big for my C20 6cyl. I used all the brake lines, locating the combination valve under the radiator. Where the brake lines go through the frame, there is already a hole, but needs enlarged.
The bolt holes for the crossmember to the frame are mostly the same. One hole on each side needs drilled and one hole needs slightly elongated.

[weim55]

Two specific things that I’m concerned about :

Is the spindle and caliper mount For DRW and SRW the same?

Is The track width too wide for the 69 vs ‘74?

In a perfect world I would like to swap out the entire front crossmember Complete with all of the suspension and brake components using the original C 20 springs in place of the much heavier C 30 springs.

Steve weim55 Colorado

[weim55]

Originally Posted by RichardJ

I missed the DRW in the first post and assumed he is talking about a C30 SRW (single rear wheel).

I used a '76 C30 SRW as a donor for my '67 C20 (GMC 2500 actually).
I disassembled both and selected individual parts. The C30 had a bigger sway bar. The C30 big block springs were too big for my C20 6cyl. I used all the brake lines, locating the combination valve under the radiator. Where the brake lines go through the frame, there is already a hole, but needs enlarged.
The bolt holes for the crossmember to the frame are mostly the same. One hole on each side needs drilled and one hole needs slightly elongated.

Assuming you used all of the suspension components from the C 30, Was there any change to the overall track width from the old suspension on the 67?

Steve weim55 Colorado

[Sheepdip]

Originally Posted by weim55

I have a free ‘74 C30 donor that is a factory dual wheel truck. Can I purchase single wheel rotors and run everything else to put under my 69C 20? Is it best just to swap the entire crossmember with all the suspension components at the same time?

Steve weim55 Colorado

You do not need to swap out your crossmember everything will bolt right to it. Read this thread:

http://67-72chevytrucks.com/vboard/s...d.php?t=444823

[SCOTI]

Originally Posted by weim55

Two specific things that I’m concerned about :

Is the spindle and caliper mount For DRW and SRW the same?

Is The track width too wide for the 69 vs ‘74?

In a perfect world I would like to swap out the entire front crossmember Complete with all of the suspension and brake components using the original C 20 springs in place of the much heavier C 30 springs.

Steve weim55 Colorado

The entire x-member can be swapped over or just the parts needed. On 1/2 tons, using the later x-member in the earlier frame requires tweaking of the motor mount stanchions. It's possible the larger trucks will have a similar issue.

On Square body C30/1-tons, there are 2 different types of calipers depending on the SRW/DRW options so that's a difference that needs to be considered when mixing parts.

The track width will increase going from drum to discs. Track width up front from a '69 to a '74 is minimal per side (.5-.75" greater).

[weim55]

Thanks for the information guys, exactly what I was seeking .

Steve weim55 Colorado