Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

A Step By Step Guide On How To Four Link Your Truck!

Discussion in 'Center Of Gravity' started by balterbuilt, Sep 14, 2006.

  1. balterbuilt

    balterbuilt 1/2 ton status

    Joined:
    May 10, 2004
    Posts:
    385
    Likes Received:
    0
    Location:
    Santa Rosa
    Well, here it is, a step by step guide on how to four link your rear on a chevy. The fallowing is just recomendations and not the only way to perform a four link. You might see things you want to do a little different, but this will help you with most questions I see on boards. If you fallow this guide you should have a good and affordable linked rear suspension.

    So, what is it? It's a double triangulated four-link, it will work any suspension you like, coils, coilsovers, quarter ellipticals, or airbags. The links will be suffictent enough to drop the truck on them without damage and you can expect (with adequate coils) 20" or rear travel.

    You will need to be a GOOD FABRICATOR to complete this, please don't attempt it unless you make good consistent welds and joints. This is your suspension after all.

    The vehicle this was designed for runs 37-38” tires and a relatively low ride height.

    Tools required: Grinder, wrenches and sockets of all sizes and shapes, a good welder, AT LEAST a 175 or larger MIG, chop saw that cuts 45*, two large jacksatnds and two small jacksatnads (under the axle) and some small lengths of 2x4 woods to put under the sants to adjust height, a ratchet strap to hold the pinion angle, a little know how would help too

    Tools not needed but help: plasma cutter, tubing bender, band saw, auto cad

    At the end is a materials list.

    I'm not including pictures of steps that I feel don't need pictures...

    Step 1: Remove your old suspension. Support the truck with large jackstands! these stands are going to be under the truck for while so make sure you wont need them anytime soon.

    Step 2: Adjust the truck to the ride height you want. This is simple, by now you should know what size tire you are going to run, or are already running. Now decide how much clearnace you want. Remeber these tires will be moving a lot under your rig, so make sure you leave adequete clerance or are prepared to cut some sheetmetal! To adjust ride height I made my upper coil spring buckets adjustable.

    Step 3: Building your suspension mounts. I recommend building your suspension mounts next. It is best to know how big they will be before you start plotting where your links will go. You don’t want stuff to get in the way. Here is an example of my coil mounts…

    [​IMG]


    Make sure you use no less then ¼” material everywhere on the suspension!!!!! This includes the suspension mounts.





    Step 4: Find your measurements. Download the four link calculator. Everything up to now has been easy. This is where you need to start plotting your suspension. You will probably need to remove your exhaust to clear the links. Here is some help with the calculator.

    To find your center of gravity, it is common to measure from the ground to the top of your transmission bellhousing. This is a safe number to use.

    For most of the other numbers in the first column you need to just do some research to find the approximate weight.

    In terms of geometry, if you are running a short wheelbase rig you will want an antisquat of around 60-70%.

    You will want a roll axis between 0 and -2*

    Your instant center x-axis should be around 140 inches.

    There is no right number anywhere here, just get it close and you’ll be ok. These aren’t road race cars we’re dealing with. Once your front tire climbs and obstacle and your rear axle articulates your geometry is and center of gravity will be all out of whack.

    For the links, I kept mine at 34” for my lowers and 29” for my uppers.

    Upper links: start dead center with center of axle tube
    At the frame: 20” apart, 29.5” off the ground
    At the axle end: 10” apart 28.25” off the ground

    Lower links: start 3.5” forward of axle centerline
    At the frame: 14” apart 21.75” off the ground
    At the Axle: 32” apart 17” off the ground

    If you plan on larger tires or a taller ride height your numbers might be a little different. Ask questions if you are confused, I can help you with your numbers.

    Make sure nothing is going to get in the way, I used the stock crossmember to build me new frame crossmember off of, you can use that as an idea of where your links will mount to.

    Step 5: Build your bridge. Once you’ve got an idea of what your links measurements will be you can build your axle bridge. The bridge needs to be very sturdy. I built this one out of 2x3x.250” rectangular tube…

    [​IMG]
    [​IMG]
    [​IMG]


    The bridge should be about 1.5” shorter then the mounting height of your upper links at the axle end if your using bushings. If your using heims or super flex joints then you will need to allow at least ¾” of clearance under the rods ends for movement of the links.
    Makes sure you welds are GREAt and you joints fitment is perfect. You might consider taking some tube that, when cut in half, will fit over the axle tube and welding it on the tube to reinforce the axle where the bridge meets it. Make the sleeves about 10” each side. It’s cheap insurance.


    Step 6: Build your frame cross member. This is a tough one. I integrated mine into my stock crossmember. Use the same material that you used in the axle bridge, 2x3x.250 wall rectangular tubing. This needs to be strong, your upper AND lower links will be mounted to this!!! The location is not super critical because your link mounts will reach out from here and “grab” your links. Just make it within a few inches of your links final locations.

    [​IMG]
    [​IMG]


    Step 7: Building your links. Here is something fun. Your links should be made of the highest quality materials. The tubing should be no smaller then 1 ¾” x .250 wall DOM tubing. For larger heavier trucks running huge tires, hardtops, etc. you should use 2” .250 inch wall DOM tube. This crap is $$$$ so get just enough.

    The rod ends are up to you. I used bushings at the axle end for a smooth and quiet ride. For the flexy joints, I used QA1 ¾” heims with high misalignment spacers on th e top links and rubicon express 2.5” super flex joints on the lower links. You gotta remember that your lower links will be taking a beating, where you lower links wont be taking any impacts. So you lower links need to be make of more durable material. If you don’t hace a tubing bender, or your’s wont bend heavy wall or chromoly tubing then I would recommend 2” 3/8 wall DOM tube for your lower links. Spend some extra coin here cause you don’t want bent links in the middle of nowhere!!!!

    This is how ibuilt my lower links to add extra strength…
    [​IMG]



    Make sure your links are the same length!!!!!!!!!!!!!!!!!!!!! Take your time and do it right.

    Step 8: Squaring your axle and setting driveline angle. To square up your axle you will probably want to have a friend help you. Find a point on your truck (I used my gas tank) to measure for side to side alignment of your axle. Use your front axle to square off of the front to back alignment. Make sure your axle is square, you don’t want it “crab walking” down the road.

    Set up your axle where it will be with the tires on. Measure your tires a take the radius (half the tires height) and set the center of the hub at that height on jackstands. Now set your pinion angle. Do not build in some slack for axle movement because now that you have links your pinion wont be rotating due to spring wrap.

    Step 9: Building your mounts. Now that your crossmember and axle bridge is welded on and your axle is square you can start mounting your links. Taking your measurements from step 4 you find how your mounts should look. Take some flat plate and some scrap tube of your choice and wled stands that are the height the links should be to mount. Minus half the rod ends height. This will allow you to hold the links to the truck and still have both your hands available to build you templates. Believe me these stands are life savers and help keep things accurate.

    Do one link at a time. You will use the same links mounts on the driver side as you do on the passenger side, so you only need to make one set of templates. Put your links on the stands and position them to where they are supposed to sit once the truck is done. Take some poster board and start cutting templates to hold your link mounts. The more time you spend making templates the better the finished product will be. Make everything strong and larger enough. Make sure that while your suspension is rotating that your links for contact the mounts.

    Tack weld you mounts in place, DON”T WELD THEM IN. If something doesn’t work you don’t want to be cutting anything apart. Welding the mounts is one of the last steps.

    [​IMG]



    Step 10: Cycling. Not a bicycle. Once you have all your mounts build and in place you can now jack up the rear end and remove the jack stands. Have a little fun and enjoy the fruits of your labor so far. Put the floor jack under the pumpkin and move the axle around to make sure it flexes like you want and doesn’t bind up. Check everything, including your driveline. Make sure it has enough travel and doesn’t bind the u-joints. Take pictures :-]

    [​IMG]


    Step 11: Gusseting!!!! This is critical. Once everything is working well and nothing is binding you are good to go. Weld your mounts up and anything else that hasn’t been welded yet. Now that you have your mounts built you need to build triangle gussets so nothing will bend or tweak. Gusset everything you can, these are easy and cheap to build so the more the merrier. This is where a plasma cutter makes your life easy, but a grinder will cut em up no problem.

    [​IMG]


    Step 12: Driving it the first time. Drive it slow at first, just take it around the block, if it makes it your probably going to be ok. This time hit the gas a little and swerve a little. Once you’ve feel like it’s driveable wheel the crap out of it.

    Materials list:

    10’ of 1 ¾” x.250 wall DOM tube
    6’ of 1 ¾” x.120 wall chormoly tube
    10’ of 2x3x.250 rectangular tube
    One 2x4 foot sheet of ¼” plate for making mounts and gussets
    Two ¾” QA1 rod ends with tube adapter and high misalignment spacers
    Two 2.5” rubicon express super flex joints and assembly tool
    Four energy suspension poly bushings
    Two coil springs
    Necessary bolts, nuts, and washers.










     
  2. MTChevy

    MTChevy 3/4 ton status Premium Member

    Joined:
    May 6, 2005
    Posts:
    7,141
    Likes Received:
    78
    Location:
    Great Falls, MT
    i like it!
     
  3. 85mudblazin

    85mudblazin 1/2 ton status

    Joined:
    Mar 26, 2004
    Posts:
    3,951
    Likes Received:
    0
    Location:
    Austin,TX
    Just to add to the thread another VERY important part is to understand Anti-squat. Not enough anti-squat will make the rig well squat alot. This can be very bad on steep climbs. If it squat alot it will roll you right over backwards. To much anti-squat and your back end will lift up giving you very little traction in the rear. A good neutral number is 100% anti-squat. This will cut out alot of the bounce and make the rig hook up very well.

    Good write up though.
     
  4. balterbuilt

    balterbuilt 1/2 ton status

    Joined:
    May 10, 2004
    Posts:
    385
    Likes Received:
    0
    Location:
    Santa Rosa
    i would say more around 70% like i had mentioned in the article. Too much antiswuat on a short wheelbase rig will cause the rear axle to try to walk up under the vehicle. i think I have like 72% with extremely soft springs and my rear end doesn't sink at all when I gas it. You don't want any less then 70% though IMO
     
  5. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

    Joined:
    Dec 24, 2000
    Posts:
    2,690
    Likes Received:
    0
    Location:
    Bakersfield, CA
    Well I thought I didn't know what I was talking about and you were the master with your funky 3 link you were running? :D

    Looks like you've come along way and you took my suggestions on most of the things. Looks pretty good.



    Huh? Is that for a blazer or what? Because that number is meaningless without knowing the center of gravity on the vehicle and every vehicle will be different. I know you stated that other vehicles will change some things but the way you wrote that it seems like it's a set number and not a variable.

    As far as antisquat, the target percentage is going to be different for different wheelbases. The longer wheelbases will want a higher # while shorter will want a lower #. This is speaking for trail and crawling and would be different for other things but most of us will be wheelin

    Maybe you want to talk a little about axle steer and torque steer and all that good stuff since that is the #1 thing I see screwed up the most on 4 linked trucks. It's awesome watching a truck trying to climb a rock with the front tire and the rear axle walks under the truck and tries to flip it over...
     
  6. balterbuilt

    balterbuilt 1/2 ton status

    Joined:
    May 10, 2004
    Posts:
    385
    Likes Received:
    0
    Location:
    Santa Rosa
    wel l iwas stating that this was designed around my truck, and being that htis is a k5 blazer based website, that's what most of those numbers are for. I do beleive, correct me if i'm wrong, that you want your instant center x-axis to be around 125-150% of your wheelbase. Also I think I mentioned it, but your center of gravity is (roughly) the top of your transmission bellhousing. I also mentioned that this set-up was for a vehicle with 37-38" tires and around teh same lift height i'm running OR your numbers will be a little different. But if you want to explain some stuff for people go ahead, it'll save me time :-P

    As far as the axle walking under your rig part, i've never seen only heard of it. But the more antisquat you have the more your axle will try to walk under your rig because the power from your drivetrain is actually pushing your rear suspension down and thrusting hte vehicle forward (think funny car). This will in turn cause the axle to try to push the vehicle up over a rock and make the axle move "under" the truck which could cause a severe shift in the vehicles weight cause it to try and roll over (depending on how severe the situation is).
     
  7. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

    Joined:
    Mar 5, 2001
    Posts:
    15,680
    Likes Received:
    1,391
    Location:
    642 Days to BB2018
    100% A.S. is not a good neutral number....and any A.S. value that you choose on level ground is going to be a LOT different (larger) once the vehicle starts climbing a hill....

    ALSO:

    I will make a prediction that the lower link mount bracket will be the first failure point of this suspension buildup. There is a lot of material removed from that bracket.....and, while "artsy"....I suspect it will buckle under the actual loads of real-life use. :eek1:

    :usaflag:
     
  8. 85mudblazin

    85mudblazin 1/2 ton status

    Joined:
    Mar 26, 2004
    Posts:
    3,951
    Likes Received:
    0
    Location:
    Austin,TX
    Which is the reason to make your mounts adjustable;)
     
  9. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

    Joined:
    Mar 5, 2001
    Posts:
    15,680
    Likes Received:
    1,391
    Location:
    642 Days to BB2018
    ....and to not even use 100% A.S. as a target in the first place! ;) ;)
     
  10. balterbuilt

    balterbuilt 1/2 ton status

    Joined:
    May 10, 2004
    Posts:
    385
    Likes Received:
    0
    Location:
    Santa Rosa
    those lower link mounts are plated front and back now, unlike in the pictures, i'm sure they'll be just fine.
     
  11. whiteknight

    whiteknight Registered Member

    Joined:
    Dec 26, 2006
    Posts:
    40
    Likes Received:
    0
    Location:
    Lawrence,KS
    Hey Im new to this forum, but i was wondering if you have any flex pics of you rig with the 4link
     
  12. balterbuilt

    balterbuilt 1/2 ton status

    Joined:
    May 10, 2004
    Posts:
    385
    Likes Received:
    0
    Location:
    Santa Rosa
    i do, but they are REALLY small pics...

    [​IMG]
    [​IMG]

    after that first outing we tore the truck apart and are changing lots on the body (bobing it, narrowing hte front, exo, etc.)
     
  13. LUBA

    LUBA 1/2 ton status

    Joined:
    Jan 16, 2002
    Posts:
    127
    Likes Received:
    0
    Location:
    Bay City, Michigan 48708
    Dumb question but why 4 link? What are the pro's and con's of doing this. Is this just to cure axle wrap?
     
  14. LUBA

    LUBA 1/2 ton status

    Joined:
    Jan 16, 2002
    Posts:
    127
    Likes Received:
    0
    Location:
    Bay City, Michigan 48708
    Never mind I figured it out?
     
  15. balterbuilt

    balterbuilt 1/2 ton status

    Joined:
    May 10, 2004
    Posts:
    385
    Likes Received:
    0
    Location:
    Santa Rosa
    sorry i don't get around very often anymore, but any questions about hte link suspension can be e-mailed to me directly at balterbuilt@hotmail.com i'm more then happy to answer any questions about any link style suspension :-)
     
  16. muddybuddy

    muddybuddy 3/4 ton status

    Joined:
    Jan 29, 2004
    Posts:
    8,933
    Likes Received:
    1
    Location:
    Fairfax Station VA
    hey man, what coils did you use and how much did you achieve with them? i know it will vary based on where the mounts are, but i just want a ball park figure. im going to be 4linkin the rear of my full-bodied k30, i plan on using 6" bronco coils, and use 2"x.375 dom for uppers and 2.25"x.375 dom for lowers. im looking to get 7-7.5" lift and run 42" tires. its going to be stock long bed wheelbase ~131"

    can you help me out with some of my geometry? if you get a chance that would be sweet! if not, ill continue to play around with some of the online calculators i have found on other sites. thanks
     
    Last edited: Apr 24, 2007
  17. Uzaree

    Uzaree Registered Member

    Joined:
    Jan 5, 2006
    Posts:
    18
    Likes Received:
    0
    Location:
    Mississippi
    As a side note.

    You can also sleeve your main link tube with another tube that fits inside the first tube to make it stronger. This is just and example but a 1.75" x .120 wall DOM will fit a 1.5" x .120 wall DOM tube inside it perfectly. That gives you .250" wall with tube memory of two different tubes. Tube memory is the ability for the steel to return to its original state after its been bent. If you bend it to far then your just screwed anyway.

    I use the Evolution 1 1/4" joints on all the link systems we do and while the tube we use is large I still sleeve it.

    Just my $.02
     
  18. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    Actually, just to be clear, sleeved tubes of a given diameter/thickness will always be weaker than a single tube of the same diameter/thickness. And that includes yield in bending and point (dent) failure modes.

    Which is not to say sleeving won't work, my own tie rod is sleeved with 1010 1.75x0.120 HREW over 1028 1.5 x 0.250 DOM, and it works just fine. But it would be stronger is solid wall...
     
  19. Uzaree

    Uzaree Registered Member

    Joined:
    Jan 5, 2006
    Posts:
    18
    Likes Received:
    0
    Location:
    Mississippi
    What I was saying was, say if the requirement is 1 3/4" x .120 wall we sleeve it with something else. By no means was I implying someone needs to substitute the correct requirement by using 2 thinner tubes to get the correct required tube thickness.

    Just to be clear :D
     
  20. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    Yeah, I figured that's what you meant, but it was the final comment about " tube memory of two different tubes" that made me feel the need to clarify. I was just afraid it sounded too much like "so it will be stronger" and didn't want folks new to this stuff to get it confused.

    In my case, it was almost exactly as you say. On the ends I wanted 1.5 x 0.250 for use of weld in bungs, and thicker wall larger OD was too much money to justify. And still, I wanted larger diameter (for those that don't know, diameter helps more than wall thickness to resist bending, though not for resisting denting) in the center, so sleeving was a good option to increase the resistance to forming a taco without adding much money to the project.
     

Share This Page