5 Lug & Disc swap

[OkieGMC]

Hey everyone I'm new to the site, been following for a little while though. Ive got a 68 LB GMC that is currently 6 lug and drum brake all the way around. I know there are several sites that have disc brake conversions as well as 5 lug conversions and Ive also read quite a few things throughout the site I just cant make up my mind on what would be cost effective.
My question is to those that have done it, what is the best route to take to doing it all?
I plan on doing a 3-5 drop on it as well if that makes any difference.
Thanks!

[PanelDeland]

If you want to drop 3 or more in in the front my personal preference is to use spindles.They give you 2 1/2 drop and require less shimming to align.So with a 1 in drop spring you get 3 1/2 drop in front.Springs also stay tighter in the spring cups.You can get the rotors in either 5 or 6 lug.The other option is to get a 72 up disc setup,rebuild it and use drop spindles.The parts are usually a little cheaper butit takes a bit more work to swap parts or the crossmember,then you still have to do the spindles.
For the rear,I would just do a drop spring/block combo and swap in a 71-72 rear.

I would strongly suggest you rebuild your front suspension while you're there.You don't really want to do it twice so plan your budget that way.One advantage to a disc kit is that you only have to remove brake parts and spindles,so if the suspension is good you don't have to replace anything.I did ball joints and tie rod ends(bushings were good)and had to replace the wheels (for clearance on the rotors) so it made a huge difference in handling,ride and overall driveability.
So plan $$$ for wheels(maybe tires),suspension parts(if you need them) and the drop you decide on.

[CC69Rat]

Just a couple things to note:

while I agree with Panel, --

The 68 rear end housing you have is likely shorter than a 71-72 rear end housing. When they converted these trucks to disc in 71 the front track width is about .75" wider on each side due to the rotor hat thickness I believe .. ? But ..

67-Early 69 6 lug housings are 55.5" long if you measure from backing plate to backing plate.

Late 69 / 70 6 lug can be 55.5 or 57" long. around the 70 models will be a transition year. My 70 GMC has the later housing in it

71+ are 57" long in the same measurement.

So, if you swap in a 71+ rear end it will change the offset of your wheel where it sits in the fender. If you're lowering it, chances are you're going with bigger tire / wheel combo (I am guessing) .. I just wanted to note that the later 5 lug housings are .75" longer on either side. 55.5 / 57" backing plate to backing plate.

So, if you go with 5 lug axle swap .. you want to make sure you know what housing you have in it now. Being 68, my guess would be 55.5" So, if you get the wrong axles .. you get the idea.

If you go with dropped spindles in the front make sure you get the correct ones. Your steering setup (tie rod ends, sleves, and center link) will also need to be replaced with the 71+ stuff if you use 71+ dropped spindles.

Again, all of it is available for your truck. My suggestion is to call Stan at Early Classics. Super cool dude and he'll take good care of you.

Yes, spindles all the way. you can get by with cutting one turn out of your front coils too but like Panel said above by cutting your springs it will make it more dificult to align later on (not impossible, .. just more difficult than spindles) another thing to consider your original factory coils have likely weakened over the years. A 1" drop spring (new) might give you the same overall height as a weak factory spring.. ask me how I know

.. Good luck man. Just thinking out loud (because I'm about to do the same thing to my GMC!)

[TobyArnot]

Welcome aboard. I will echo what the above have said. I used the 2-1/2" spindles and cut one coil on my '70, but found the front was too low for a DD. Went back to stock springs and a smaller front tire. Also 4" springs in the rear. FYI

[67chevemall]

Stick with the 6 lug. Drop spindle and disc brakes swap up front. And just air bag all four corners.
You can run schrader valves on each bag until you have more funds for the compressor and valves. www.cpp.com and ***************** will fix ya up.

$0.02

[mrhino]

Iv done several disc conversions now. and the best way iv found is drop spindles. use suspension parts, like ball joints and tie rods from 73-80 somthing c/10s. Buy new coils in whatever drop you want. For the rear. Dont pull out your rear end and swap it way to much work. Either buy new axles from Moser engineering with 5 lugs (they have them ready to go) or send them your old ones and they will redrill them. get your self some rear disc brackets. (I think someone on the form here sells them). get the recommended rotors, calipers, hoses, and pads for the brackets you got. put it all together and your done. its easy. Oh ya dont for get a new proportioning valve

[EddieB383]

I'm in a similar situation with my 69 GMC swb. I have drums all the way around, but I would like to lower it and swap to a 5 lug disc brake set up. I figured I would go ahead and get one of the many drop spindle and 5 lug rotor conversions since the brakes are shot anyways. I wouldn't mind having drums on the rear for now, but I would need 5 lug rearend. My truck is a leaf spring truck and I know the leafs are narrower on these so I wasnt sure what year rearends would interchange. I'd like to find a 12 bolt leaf spring 5 lug rearend off of a 71 or 72, but around here that can be a bit hard to locate. That is my major issue. Also, will I need a new proportioning valve when I swap the front to disc?

[lolife99]

Originally Posted by EddieB383

I'm in a similar situation with my 69 GMC swb. I have drums all the way around, but I would like to lower it and swap to a 5 lug disc brake set up. I figured I would go ahead and get one of the many drop spindle and 5 lug rotor conversions since the brakes are shot anyways. I wouldn't mind having drums on the rear for now, but I would need 5 lug rearend. My truck is a leaf spring truck and I know the leafs are narrower on these so I wasnt sure what year rearends would interchange. I'd like to find a 12 bolt leaf spring 5 lug rearend off of a 71 or 72, but around here that can be a bit hard to locate. That is my major issue. Also, will I need a new proportioning valve when I swap the front to disc?

yes.
And you need a new m/c for disc brake trucks.

[lolife99]

Originally Posted by OkieGMC

Hey everyone I'm new to the site, been following for a little while though. Ive got a 68 LB GMC that is currently 6 lug and drum brake all the way around. I know there are several sites that have disc brake conversions as well as 5 lug conversions and Ive also read quite a few things throughout the site I just cant make up my mind on what would be cost effective.
My question is to those that have done it, what is the best route to take to doing it all?
I plan on doing a 3-5 drop on it as well if that makes any difference.
Thanks!

Read this:
http://67-72chevytrucks.com/vboard/s...68&postcount=4

[EddieB383]

Originally Posted by lolife99

yes.
And you need a new m/c for disc brake trucks.

Thanks for the info...will I be needing a new booster and master cylinder or just the master cylinder?

[OkieGMC]

Thanks for the info everyone! Definitely a lot of options to consider.. Here recently i've thought about just keeping it 6 lug if i could find a nice set of wheels I like and save me a lot of the headache. Theres quite a bit more involved than i thought.

Lolife I think ive read that a dozen times and thats how i feel after

What would you guys think about swapping everything from a 74' front and rear? Too much or am i just making this too difficult?

[Leroy-B1]

its a shame your not closer I have a complete 72 swb frame with disc brakes and front sway bar I would let go for 200 bucks....would be cheaper just to swap it out and then add drop kit