ISO front spindles, 8 lug, have ?????????

Discussion in 'Lifted & Offroad Suspension' started by 77p20, Mar 6, 2011.

  1. 77p20

    77p20 Member

    i am restoring a 77 chevy grumman step van.
    it has 8 lug drums all 4 corners, i am wanting to convert to disc on the front.
    i understand the p20 is based on a same year c20 3/4 ton long bed frame, is this correct?
    it has IFS and looks same as parts on those era trucks, but i was told today that the ball joint angles may be different, or have a different taper on the shaft...... i cant see that minor of a difference on stock parts, but dont know enough to know so i am asking for any info you guys may have on these set ups

    i found disc spindles, but am afraid to go drop the money on them if they wont work (salvage yard, so no refunds)

    ---------- Post added at 10:40 PM ---------- Previous post was at 10:39 PM ----------

    was there a separate commercial frame, or a motor home frame these vans were built on? would these parts be different from a same year span c20 or suburban?.... i remember someone over the weekend mentioning a camper special........ were the geometries really different on all these?
     
  2. Crawdaddy

    Crawdaddy ↑↑↑ Has no life Staff Member 5+ Years 1000 Posts Platinum Contributor

    I would think there's a C/K drum to disc conversion for the front that you could apply to your p20. GM typically doesn't change too much between models like that.
     
  3. 77p20

    77p20 Member

    are you talking about J/Y parts? because i have searched endlessly for a store bought kit and have come up empty handed.....
    tomorrow is monday, so i can go to oriellys and sit with the guy comparing parts, but thats going to leave me liable for supplying the beer at the next company party, lol

    ---------- Post added at 11:14 PM ---------- Previous post was at 11:13 PM ----------

    excuse the ignorance, but when you say c/k your talking about c series trucks and k series suburbans right ?
     
  4. Crawdaddy

    Crawdaddy ↑↑↑ Has no life Staff Member 5+ Years 1000 Posts Platinum Contributor

    I was refeering to a kit made by a company. I was assuming one existed, but if you've searched, I stand corrected. The junkyard would be a good starting point to find parts that could do the job. C/K refers to the pickup truck or suburban line. C is 2wd, K is 4wd. The P series should be 2wd, so looking for a 1973-1987 C series 3/4 or 1 ton pickup with front disc brakes should be a good start to find the parts you need. The half ton parts will be different in regards to ball joints, spindles, brakes, etc will not be compatible.
     
  5. 77p20

    77p20 Member

    sweet, yes, the p20 is a 3/4 ton SRW configuration, so i figured 1/2 ton parts would be out of the equation, and if i remember right, a lot of 3/4 and whole ton parts were the same....and yea, i said search, but just webpage to webpage sort of searching.... have stopped asking people on the phone because i get different answers to the same questions, and most leave me with more questions as well

    from what i understand, i am looking for "C" series parts, 3/4 ton, 8 lug....what was the difference between 6 and 8 lugs ? ive seen plenty of 3/4 ton stuff with just 6, but have also seen with 8 as well.....

    thanks for the help so far crawdaddy

    im really looking forward to getting some discs on the front of this thing this week, at same time i restore the system itself(new booster/master cylinder/etc...)
    she weighs an even 5k when empty, and im planning on using all of her 7600gvw when done.......
     
    Last edited: Mar 6, 2011
  6. Crawdaddy

    Crawdaddy ↑↑↑ Has no life Staff Member 5+ Years 1000 Posts Platinum Contributor

    6 lug 3/4 ton trucks are, at least by me, considered light-duty 3/4 ton. Oxymoron, I know, but here's my reasoning. The 6-lug 3/4 ton trucks use 14-bolt rear axles, but they're only semi-float axles. The axleshafts hold the weight of the truck, whereas with a full-float axle, the axleshaft's only duty is to rotate the tires. Now, how does this apply to you? While 6 lug front end parts would likely work if you used 8 lug rotors, I wouldn't take the chance. Just find a 3/4 or 1 ton and pull from the spindles out. Spindles out would include the spindle itself, the rotor, caliper, wheel studs, basically everything on the front end except the control arms, and if it's a nice pull-a-part yard that has real good prices on parts, grab the control arms too. It's easier to get rid of scrap steel and iron in the form of uneeded parts than it is to source that control arm that you left at the junkyard because you were sure the ball joints would match with the spindles you got...ask me how I know...

    ---------- Post added at 11:20 PM ---------- Previous post was at 11:08 PM ----------

    One thing I just thought of is you'll also have to adress the brake system. You may have to switch out your proportioning valve and/or brake booster/master cylinder, or add an adjustable brake pressure valve for the front brakes. I'm not quite sure how far you'll have to go for that, perhaps someone else (tbplus10 in particular) can help you with that.
     
  7. stephan

    stephan Rockstar 4 Years 5000 Posts

    When I was looking for a spindle lift for my C3500 & couldn't find one cuz nobody makes one :grrrrrr: I started checking to see if I could make 3/4 ton spindles fit & I researched the ball joint part numbers & they are not interchangeable at least according to part #
    At that point I quit looking, but if you happen to solve the ball joint problem, you will still need to check wheel bearing to axel fitment & tie rod ends. The brake calipers I didn't figure would be a problem because I could make mods for the mounts but I never got that far since I struck out on the ball joints. The diameters of the tapers are going to be larger on the 3/4 than the 1/2, & the 1 tons will be larger than the 3/4T
     
  8. 77p20

    77p20 Member

    ok, that makes sense and is what ive heard from a couple of others about the ball joints being different........soooooooo......... if thats the case, can i do what CRAWDADDY said (Just find a 3/4 or 1 ton and pull from the spindles out. Spindles out would include the spindle itself, the rotor, caliper, wheel studs, basically everything on the front end except the control arms, and if it's a nice pull-a-part yard that has real good prices on parts, grab the control arms too.)
    if i get the entire assembly, which is what i was planning on doing, and get the control arms as well, would that end any questions as to interchangeability ? if i have to choose a 1 ton donor, or would i just be relocating the questionable area to a different location ?

    ---------- Post added at 01:25 AM ---------- Previous post was at 01:13 AM ----------

    ok, you confused me on this one ? this is a 2wd IFS van.
    you're talking about the spindle right? would the bearing not be the same on an 8 lug 3/4 ton and an 8 lug 1 ton ? i cant see chevy having that many specifically different parts....
    ford yes, but not chevy from my experience so far
    as far as tie rods go...... if the donors are larger diameter, can i grab the rods on both sides of the adjustment sleeve and it bolt up properly if same length?

    im gonna need a bigger boat.....
     
    Last edited: Mar 7, 2011
  9. stephan

    stephan Rockstar 4 Years 5000 Posts

    If you have a friendly salvage yard that will let you go in the yard & measure before you buy, then measure where the A arms mount to the frame. (Measure your van before you go). If the mounts to the frame are the same on the donor truck as your van, then definitely buy the A arms too cuz it's a cake walk from there on out cuz there won't be any fitment problems. I never got this far because the yards here won't let you in to look. You just have to buy sight unseen & unmeasured.

    Yes, I was talking about fitment from wheel bearings to spindle. From 8 lug 3/4 ton to 1 ton there is some difference in wheel bearings but the GM parts boys wouldn't tell me what it was (they may not have known, or maybe just didn't want me modifying my truck since GM Corporate & most dealerships don't) but they showed 2 varieties of front wheel bearings for the 3/4 tons, the difference was due to GVWR, & even the 7K rated one was a different part # than what they showed for mine which is also a 2WD, IFS but it's a C3500 1 ton.
    On your tie rod question..I don't know. I would definitely grab them (the complete tie rods, not just the ends) off the donor truck, & possibly the rod ends will screw into your adj sleeves. If not then at least you have extra parts that you can mix & match (we know the ends will fit the steering knuckles because they're going to be off the same donor truck) but the sleeves may be smaller or larger diameter. Like CDaddy said buy everything you think you'll need, don't leave it sitting in the yard cuz by the time you figure out you need it, it may be gone.
     
  10. 77p20

    77p20 Member

    great info guys, thanks a lot!
    ive been googling different key words all night looking for whatever i could find....... here is the best explanation i could find that caused me to understand a bit better if this swap will work.....

    "That is correct. You can bolt a 1/2 ton lower controll arm into a 3/4 ton or a 1 ton Chassie. Or a 1 ton into a 1/2 ton. The front cross members have all the same dimentions from 1960 to 1987. Which means that any combination of front suspension parts will interchange. So if you have a 3/4 ton truck and want to change it over to 1/2 ton front suspension, all you have to do is change the 3/4 ton "Lower controll arm" to a 1/2 ton "lower controll arm" get the correct ball joint size. You can leave the upper controll arms in and just change out the 3/4 ton upper ball joint to a 1/2 ton ball joint for either Drum or disc brakes. Any spindle C-10, C-20, C-30 will work as long as the upper and lower ball joints are for that spindle. Now to get it to steer you will need the correct steering linkage. Inner and outer tie rod ends and sleve and center link for the year of spindle that you are using. For instance, if you come across a pair of spindles from a 1975 C-10 and want to install them on your 1966 C-20, you will need the complete steering linkage from a 1973 to 1980 C-10 and upper and lower ball joints for the same year, and change out the 3/4 ton lower controll to a 1/2 ton lower controll arm from any C-10 up to 1987. As far a steering arms (idler arm or pittman) check the fit into your newly acquired center link. I'm sure that this info will raise a lot of questions and doubt, but be assured that this info is correct. I have over 30 years of doing suspension on these trucks and have tried every combo there is to be tried. Please ask me any questions that will come up."

    with this and what you guys shared here, i am a lot more confident about hitting the salvage yard later today :)
     

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