73-87 disc brake help!

[calvinator]

I bought an 84 gmc half ton for a parts truck. I am wanting to swap my truck from 6 lug drum to 5 lug discs. Today my dad and I removed the entire front end. (brakes, A-frames, etc.) but I think we removed more than we needed just to be safe. I plan to bring them to a business in town to get everything sandblasted and powder coated black. (I used to paint there so I may even get it done free!) So now I need to know which parts to actually use and how much custom welding/fabricating is needed? If someone has done this could you please PM me and list it in great detail? Also, I plan to buy drop spindles, so now would be the time to install them right? Any info at all would be very helpful.

[calvinator]

Guess it may be helpful to know i have a 1970. Whether or not that makes a difference... And what are my options for the rear axle? Swap the one off of the 84 onto my 70? I heard they might be a little longer, is that true? Is there a place to buy a beefed up rear end that would fit my truck? Thanks

[lolife99]

Do some "searching" in the suspension section. You can use all of it,... or leave the actual crossmember in your truck, and swap everything else. I would look for a 71-72 rearend or buy some conversion 5-lug axles for your 70 rearend.

[70GMCer]

Mine is a 70 & I just went thru this setup. That whole setup you have will bolt right in, but Keep in mine, if you are running sbc hedman headers, the lower control arm bushing nut will not clear them. For that reason, I ended up using the original arms with new 73/87 ball joints. I used the 84 spindles, 73/87 outer tie rods & rebuilt the rest of the parts using, 71/72 upper & lower controls arms with 73/87 ball joints, 71/72 drag link, 71/72 inner tie rods. Also pay attention as to how the drag link & tie rod ends come apart. The center drag link will fit in backwards & you not know it. I didn't know this when I did mine. If you have the drag link in backwards, you will get severe tire dragging/squealing on sharp turns. All these parts are for the 1/2T

[mkundo]

GMCer,
That is great information, I have a '71 with '73- '87 components myself.
Have fun working on your truck and spending time with you Dad makes it even better.

[lowriden58]

what rear end do you have? 12bolt? if so i have some 5lug axles i just pulled out

[jorgensensc]

my '68 has a later model front crossmember/disc setup. If t was me I would take the whole thing apart. Also if you want drop spindles you will have to have the 1 1/4 brake rotors and matching calipers. They do not make drop spindles for the 1" rotors. They are relatively cheap from the parts store and all you need are the rotors and calipers. The brake pads can be reused (mine were almost new) I would power coat everything individually if it were me. I think it is a great upgrade though!
Shawn

[jorgensensc]

Your 5 lug axles may not fir his 12 bolt. Somewhere in 70 they changed the length of the axles. Some 70's have the shorter 67,68, 69 axles, some have the longer 71, 72 axles. You need to measure before you try to throw them on there. Just being helpful.
Shawn

[calvinator]

Thanks for the info guys. No I dont have headers on my truck. So is it easier to keep the original crossmember on my 70? or rather swap crossmember and all from the 84? Yah I plan to dissassemble all the components for powder coating. Someone mentioned 1 1/4 rotors and 1" rotors. Whats the difference? Whats that measurement of? Will these new rotors off ebay directly replace mine from the 84 gmc?

http://cgi.ebay.com/ebaymotors/81-87...QQcmdZViewItem

[jorgensensc]

measure the thickness of the rotor. I don't know about the ebay add, they don't explain the thickness. You are looking for the JB5 brake option (heavy duty brakes). Personally I would stay away from cross drilled rotors, they have been known to crack at the holes. Dimpled rotors are a little different but offer the same type effect.
SHawn

[70GMCer]

I would not use rotors from a source like that. Keep in mine that a lot of rotors like that are China made & may not hold up (crack or warp). Try contacting some of the vendors on here for your rotors.

[calvinator]

Someone mentioned that they dont make drop spindles for 1" rotors. I found these spindles on Ebay. Would these work for my setup? (assuming that my discs are 1" )

http://cgi.ebay.com/ebaymotors/DJM-D...mZ120038997306

[jorgensensc]

You know they just might work. They didn't have them afor 1" rotors when I was looking. Hmm.
SHawn

[franky69c10]

http://67-72chevytrucks.com/vboard/s...nt+crossmember

[calvinator]

franky, thanks a million for the link to the old thread! tomorrow I think ill take a look at the front end on my 70 and see if i can figure a few things out, now that I've got a good idea what to do. ill keep you guys updated on the progress and powder coating

[calvinator]

Im still a little confused. Sounds like theres numerous ways of swapping these parts for discs/5 lug. Should I rather re-drill and bolt the entire crossmember and all its components, OR just use as few parts as needed. Someone on the linked thread that franky left said its not even necessary to use the upper/lower a-arms as long as the ball joints are the proper ones for the spindle. If I replace the ENTIRE crossmember, is there a chance of bolting it in a little crooked? cause that would surely mess up the ride/steering. thanks

[franky69c10]

Originally Posted by calvinator

franky, thanks a million for the link to the old thread! tomorrow I think ill take a look at the front end on my 70 and see if i can figure a few things out, now that I've got a good idea what to do. ill keep you guys updated on the progress and powder coating

any time ...

[jorgensensc]

Personally, I would swap the whole crossmember. Bolting it on is easy. Two bolt holes line up and two have to be elongated. You can do it!!
Shawn

[calvinator]

4 bolts sounds a whole lot simpler than taking everything apart and mixing the different parts of the different trucks. As you can see in the first picture of this thread we just used a cutting torch to remove it. But the two "arms?" that swivel are torched off. The ones that are mounted on the 'almost-straight' bar in front (the springs are hiding behind them). sorry i dont know the lingo for all these parts, lol. But my question is: did we need those to be complete the swap? cause its too late if we did...

[calvinator]

My dad and I took a look at the front end of my truck just now and we must be talking about something else. We counted 6 bolts on the bottom of the crossmember (3 per side) and then 4 bolts (per side) on the motor mounts. Thats a total of 14 bolts, whereas Ive been told by a couple people its only 4. I want to make sure we are doing the correct thing before we start hacking my truck apart. Can anyone help?

[lolife99]

I think they meant you will have to "DRILL" 4 new holes. As in,...10 of the 14 holes,... will line up.

[jorgensensc]

Okay,
let me see if I can explain it better. THe 3 holes on each side of the crossmember (6 holes total) line up withe the bottom of the frame if I recall correctly. The 2 holes on the sides where the A-arms are ( 4holes total) the back (toward the cab) hole lines up, but the front hole (towards the bumper) needs to be elongated to match the frame.(elongated back towards the cab). I hope this helps make this clear as mud.
SHawn

[calvinator]

thanks again jorgensensc, you've been very helpful with this swap. this should give my dad and i enough confidence for trying the swap. unfortuneatly we cut the brake lines while removing the crossmember rather than unhooking them at the end so ill have to buy new ones I guess. oh well, ya live n learn.

[70GMCer]

Have fun.....

[steelhorse]

cool link