Disc brake conversion question

[aaronfab]

First, I'm sorry, I know this topic has been covered and covered and recovered, but I'm looking for some clarification before I start pulling parts. I've read the thread: http://67-72chevytrucks.com/vboard/s...ad.php?t=35042 Which changed my mind from the 73-87 5-lug swap to the 88-98 6-lug swap, because my ride already has sweet 6-lug mags. Okay, here are the specs: My truck is a '70 1/2t SWB(6-lug frt drum). I bought a '72 3/4t LWB(8-lug frt disc). And I have free picking on a '89 1/2t w/1" thick rotor (5-lug frt disc). Question: Can I use the lower A-arm from the '72 3/4t, with the spindle, ball joints, and caliper from the '89 1/2t, bolt on a new '88-'98 3/4t 6-lug disc, all on my '70 1/2t SWB???? I know about the tie rods, I'll work that out afterwards. Thanks for all your help.

Aaron

[BarryB]

I don't know the answer to your question. But is the reason you are swapping all this is to retain 6 lug bolt pattern , but also have disc brakes? I thought I would mention they make a kit for doing this with out swapping all the a arms and such. I don't have a link for it but I am sure somebody on here could get for you.

[Geezer]

I think I get what you’re asking… You could go to an auto parts and put the ball joints side by side and measure them to find out if they might work. Then measure and compare the spindles. I haven’t tried that combo but it might work… Why don’t you want to use the later model lower A arm?

[roj2323]

to install the 88 up spindles here's the list of parts.

72- 3/4 ton lower a arms
88 lower and upper ball joints
88 spindles
88 rotors
88 calipers exc.
u know about the tie rod ends so have fun with that.

the lower ball joints will press into the 3/4ton arms with no issues.

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if you go with 71-87 parts you don't have to change the a arms.

[aaronfab]

So, the '72 3/4t a-arm will work, great. But is the '88 stuff 1/2t or 3/4t? All or some? The reason I'm going with the newer stuff and not the '73-'87 stuff is I want to retain 6-lug.

Aaron

[roj2323]

well retaining the 6 lug is great but doing it with 88 stuff isin't going to work. the bolt pattern is different from what i understand. you're better off using 71-87 parts and getting the rotors with the correct bolt pattern online.
ondrew

[aaronfab]

Anyone else have any input?

[dallas71]

GMCPauls has a kit to do this using you existing A-Arms and ball Joints and it is a 6-lug setup and it is only $460 if you dont need the mc and proportional valve....if you need mc and valve i think it is $660

63-70 Deluxe 6 Lug Disc Brake Conversion NEW
3081936 63-70 Deluxe 6 Lug Front Disc Brake Conversion. Includes disc/drum brake proportioning valve w/bracket & lines, new disc/drum master cylinder, inner & outer wheel bearings, new grease seals, dust caps, calipers, brake hoses, brake pads, 12" 6 lug rotors, spindle nuts & choice of 2-1/2"drop or Standard Height spindles that use your stock ball joints and steering parts. 2 wheel drive 1/2 ton only. Will not work with some stock drum brake rims. Optionally you can add disc brake dust shields for additional $45.00 $619.95



63-70 6 Lug Disc Brake Conversion
133163 63-70 6Lug Front Disc Brake Conversion Includes Inner&outer wheel bearings, new grease seals, dust caps, Calipers, Brake hoses, Pads, 12" 6 Lug Rotors, spindle nuts & choice of Spindles(2 1/2"drop or Standard) and use your stock ball joints and steering parts. 2 wheel drive 1/2 ton only. Will not work with some stock drum brake rims. Optionally you can add disc brake dust shields for additional $45.00 $469.90

http://www.gmcpauls.com/Brakes%26Steering.htm

[aaronfab]

Dallas71,
Thanks for the info, but I want to do the 88-98 conversion, because I have free access to a bunch of junk trucks. I'm just looking for some clarification on exactly what parts I need. Thanks again.

[68fleetsidec20]

Yes, all the parts you mentioned will bolt together and work, however when I did the swap I ran into some problems. Bump steer may become an issue as the tie rods mount on the lower side of the spindles rather then the top side, this drops the tie rod by about 2"-3" increasing the angle. On a truck lowered 2"-3" this most likely wont be a problem. A bigger problem for me was the 89 spindles are aproximatly 1" taller then the earlier spindes which changes the angle of the upper A-arm and results in to much positive camber. My solution for this was to machine down the spacers that go between the spherical mount on the end of the cross-shaft stud and the cross-shaft itself, right where the shims will be. These spacers should be about .367" stock and I took them down to .200" as that seemed to leave enough material as to not weaken them. I also had to clearance the gussets in that area to keep the cross-shafts from hitting them ( you'll see what I mean when you get in there). Now my truck still has slightly too much positive camber but the front clip is off as well as everything inside the cab so the added weight should hopefull bring me into negative camber which is easily adjusted with shims. Once again if your truck is lowered you may not have this problem but I really can't say for sure. And yes the bolt pattern is the same but the studs are metric so you will have different lug nuts front to rear or you can always install new studs if that concerns you. I had posted my suspension geometery questions earlier
http://67-72chevytrucks.com/vboard/s...d.php?t=211456
and will try to update this thread with pictures when I get the chance. I know my post is long but the swap isn't actually all that difficult. Good luck

[aaronfab]

68fleetsidec20,
Thanks for the info, that helps a LOT! I've realized from researching(pulling parts at the parts store and measuring) that the "heavy half" and "light 3/4T" use the same spindle. I'm pulling the spindles, rotors, calipers, and tie rods from a '90 3/4T 6-lug. My truck will be lowered, so hopefully I can aviod some of the camber problems. Keep the wisdom flowing.

Aaron