70 C/20 Disc Brake Swap

[jamesjr]

I have a 70 c/20 with power drum all around. I also have a 87 3/4 Sub that
I'm parting out. Can I use the front disc on my 70? If so, what do I need from the Sub?

[dennislbrooks]

ttt

[junior219]

i have a 71 c 20 I am parting out and it has disc brakes on it, if you are interested

[thecatseye66]

Welcome to the board!!!:
Check out this thread in the FAQ's (lots of great information there):

http://67-72chevytrucks.com/vboard/s...ad.php?t=13692

OR, you can swap the entire crossmember, but you have to elongate (egg-hole) some of the holes in the frame to make the newer crossmember fit. You also have to use the newer MC and proportioning valve to accomodate the front discs. Some guys have gotten away without changing the MC/prop valve but the pressure is different and you will have less stopping power (which is why you'd want to do the swap anyway).

Good luck--

[70GMCer]

I've been told that you can just drop the whole front suspension, (4 bolts) and bolt it to your truck. I have a 84 Sub, and plan on doing just that to my 70 GMC...

[doug70]

I'm doing that right now, so I can't help much. I just tore down a 77 3/4 disk system. I am using the entire front end from the 77, except I tore it all down to rebuild first. Just ordered the PST OE kit today. I have most of the 77 front end cleaned and blasted. If it gets warm enough the next couple of days, I will get it all painted and ready to go back together.

Doug

[kanuck]

I'm still trying to find the answer to whether the swap is just that, remove the bolts, re and re the cross member and bolt back in. Are they an exact match or is there more to it then that. I have a '67 SWB that I would like to update to disc brakes and power steering, and finding a front suspension from a 73 to 86 is quite easy here. I know I will have to update the M cylinder and steering pump, but right now the cross member is my main objective.
Hagen

[Tx Firefighter]

Yes, you can use your later donor truck stuff.

It's just like a 1/2 ton swap is. The front crossmember is held to the frame by 14 bolts. Twelve of them will line straight up and the last two are close enough to allow slight enlongation for lining up. Just bolt up the 12 and the last two will be obvious and easy to drill since the 12 bolts have the crossmember secured and aligned.

[70GMCer]

Did I say 4 bolts?? I ment 14.........duh

[jamesjr]

Originally Posted by junior219

i have a 71 c 20 I am parting out and it has disc brakes on it, if you are interested

Thanks, I really appreciate it. If I can't use what I have I will certainly let you know. Jim

[jamesjr]

Originally Posted by thecatseye66

Welcome to the board!!!:
Check out this thread in the FAQ's (lots of great information there):

http://67-72chevytrucks.com/vboard/s...ad.php?t=13692

OR, you can swap the entire crossmember, but you have to elongate (egg-hole) some of the holes in the frame to make the newer crossmember fit. You also have to use the newer MC and proportioning valve to accomodate the front discs. Some guys have gotten away without changing the MC/prop valve but the pressure is different and you will have less stopping power (which is why you'd want to do the swap anyway).

Good luck--

Thanks for the info. I was hoping to just change spindles, tie rod ends, ball joints and drag link. I assumed the M/C and valve also. Is what you are recommending easier? Jim

[jamesjr]

Originally Posted by Tx Firefighter

Yes, you can use your later donor truck stuff.

It's just like a 1/2 ton swap is. The front crossmember is held to the frame by 14 bolts. Twelve of them will line straight up and the last two are close enough to allow slight enlongation for lining up. Just bolt up the 12 and the last two will be obvious and easy to drill since the 12 bolts have the crossmember secured and aligned.

On a 1987 everything is pretty much METRIC. Is it still going to work?
Also, The 87 is a big block and the 70 is a small block. Thanks, Jim