How technical is a rear 4-link and what are considerations?

[Jesus_man]

Well, I really love my 11-leaf rear springs. They flex really nice and are plain and simple. However, I have issues with axle wrap and have eaten more than my fair share of rear u-joints. Part of the problem is that with my Atlas, the rear driveshaft is quite steep. Also, due to Atlas, there are copious amounts of torque even when there is no shenanigans.

I have 90% of an anti-wrap kit from Barnes, but is this just a band-aid fix? I have a plan to design it in such a way that I could install it now and make it expandable for if I get push the rear axle back.

Here is my plan for the future of the bronco:
1. push rear axle back 3-4".
2. modify fenders to accommodate.
3. replace rear fuel tank with custom design to have relief for rear pumpkin and filler neck relocation.

I was initially thinking I would simply relocate the spring hangers back 3" and up 2" This would help them be tucked up higher. Gain the 2" back with a set of spring rockers. And something I feel confident I could do with simple maths.

The things holding me back are:
1. Work Space - moving this summer and have no idea yet what I'll have.
2. $$ - No idea what a 4-link may cost, but I have all but $50 worth of parts to complete an anti-wrap device.
3. Downtime - I don't want to tear into this and not be able to enjoy my bronco for years. That, and since we seem to be moving every two years now, I just can't have it down that long. I know I can't afford to hire a pro to tackle this for me.

So help me brainstorm.

[ZOSO]

well I know the duffs 4 link wont work for you unless you push the rear axle back. the frame side mounts are on the inside of the frame. they are about at the spot where your t case sits now. but I will say its totally worth it.

[Jesus_man]

That is intriguing. $1300 for a DIY kit that seems to come with the truss and the links. So I'd have to come up with frame brackets, coils, and shocks.

Another $530 gets you the whole kit minus the sway bar.

Or the dual sport kit sans sway is @$2500.

Food for thought! Thanks!

[Digger]

If you're happy with the characteristics of the leaf springs minus the axle wrap, then the anti-wrap bar would be fine for your situation.

[Strike2]

Like Digger said if your happy with the setup and have most of the axle wrap material on hand what about checking into a hi 9 third member to help the pinion angle. I haven’t researched it but might limit the down time vs taking on a complete rear 4 link set up.

[ZOSO]

That is intriguing. $1300 for a DIY kit that seems to come with the truss and the links. So I'd have to come up with frame brackets, coils, and shocks.

Another $530 gets you the whole kit minus the sway bar.

Or the dual sport kit sans sway is @$2500.

Food for thought! Thanks!

food for thought. I run the dual sport. It only requires a 1in body lift. I do not run the sway bar. Zero issues on the street. Using the duffs kit was just easy for me. I read till my head hurt on how to set up a 4 link to get the geometry correct. Still have no idea what any of it means. I will say the 4 link is so stable and awesome traction. The duffs dual sport also has poly bushings on the frame side. I wore those out after about 2k miles. 300 or so of that was dirt/wheelin. they made for a long drive home from ouray with over an inch of side to side movement in the rear axle. I have since swapped out to ballistic joints on the frame side and no more issues. Ran it pretty hard for a week in BV at super cell. Over all wheelin the 4 link is super nice. Traction and smoothness in the bumpy stuff. On road not much difference in ride quality but a little more body roll. Nothing that has scared me. Oh and I placed 2nd on the ramp for stock wheelbase. scored a 115 on day 2.

[Gunnibronco]

I looked at lots of Rob's pics as he installed his 4 link. From my perspective I don't think there was room for the brackets, etc with the length of the ZF/Atlas4 drivetrain. I don't remember exactly what jumped out at me, but I remember that I scratched it off the list of options.

I haven't had axle wrap at this point, but just bought the stuff for a traction bar for my new rear axle. I'd rather be proactive and stabilize everything before I start breaking stuff.

After talking with Gearworks, I think the high pinion 10" would be strong enough, despite running on the coast side of the gears. Their gears are strong, shot peened before heat treating, then REM polished. I just saw a Trophy truck for sale with their HP diff in the rear.

I haven't run my rig long enough to develop u-joint issues, but I made sure to set the rear pinon angle right, and I could cycle it without binding the joints. I also have a 2 or 3 extra inches in wheel base, and I left the speedometer fitting off the Atlas and used the 1/2" spacer instead of the 1" spacer to shorten my drivetrain as much as possible.

[Jesus_man]

A hi-9 has been on my list a long time! And the hp10 seems even more appealing, but can they be added to a stock BB housing? That would help considerably. But I have also always wanted more wheelbase and better departure angles. The hp10 would cause a regear on the front (not detrimental in the event I jump to 37's one day).

I suppose a new 3rd isn't throwing money away either as a diff that would last me a long time!

I'm still thinking on it! I probably need to pull my bronco out of storage and get it in the garage to take a closer look. And to inventory what I need again to complete the axle-wrap device.

Installing what I have will obviously be the least amount of downtime. Then perhaps I can decide on either an HP diff or a 4-link kit at a later date. Maybe we'll find a house with a nice shop that makes working on stuff a lot easier. Right now I have to climb all over mower, pressure washer, shop vac, snow blower, etc, to get to my tools. Not sure my wife would appreciate my taking over the entire garage this time of year.

Appreciate the input. Keep it coming.

[Gunnibronco]

The 10" gears will not fit a stock housing.

The fab'd housing is surprisingly small despite being able to fit a 10” gear. I'll measure the ground clearance compared to my stock housing and get back to you. I bet it's smaller. It's the same size as the D44 or smaller.

The rear housing isn't that complicated to build. Housing ends and spring perches is pretty much all you need. You could build it to reuse your brakes and axles if you didn't want to upgrade.

I don't expect to ever replace these axles.

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[dbasile]

I thought about linking mine too. But I am cheap. 3rd place on the rti at Super Celebration West in the extended wheel base class with leaf springs.

I got the leafs from a 99 escalade. The big deal is 5 1/2 front springs with a little less that 4 inches of lift. I moved the rear back qbout 4 inches and am just shy of hitting the crossmember or the fuel tank.

Prior to my changes I too had terrible rear wheel hop. Gone now. I also installed bigger spring perches, this may have helped.

[Gunnibronco]

I thought about linking mine too. But I am cheap. 3rd place on the rti at Super Celebration West in the extended wheel base class with leaf springs.

I got the leafs from a 99 escalade. The big deal is 5 1/2 front springs with a little less that 4 inches of lift. I moved the rear back qbout 4 inches and am just shy of hitting the crossmember or the fuel tank.

Prior to my changes I too had terrible rear wheel hop. Gone now. I also installed bigger spring perches, this may have helped.

That's awesome. 3rd place in a class that probably included some linked/coilover rigs.

I'm not sure but our trucks are the only ones I know of running the 54" GM rear springs. Seems like we stumbled on a pretty nice combo.

How did you decide to go this route? It was kind of a whim for me. I saw a chart with a bunch of spring specs and these matched weight ratings with EBs and the dimensions put the axle where I wanted it.

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[Jesus_man]

New wedges would make some sense too as I run a shim now.

Remind me what the eye-eye length is on those springs? Are they EB width too? They do flex pretty well it seems, but perhaps slightly stiffer than what I have now. I'm still game for cutting off my factory spring hangers and moving them up as my front ones seem to get me in trouble A LOT! But if the fronts can remain in the same location, that simplifies things a bit.

[Gunnibronco]

They are 54”with the perch pin centered in the leaf pack. So pushing them right to the end of the frame adds about 4” to the wheelbase. They are not EB width, they are 2.5" wide so you need all new hangers. I doubt they are stiffer than any EB spring, they have the exact same spring rate. I can't tell the difference from my 3.5” WH 11 leaf pack.



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[Jesus_man]

I actually don't know how that compares to stock EB.

But did you move your front hangers at all? I suppose you had to replace them due to extra width?

[Gunnibronco]

Stock Bronco springs are 48” eye to eye. I wonder how much better a "custom" spring could flex compared with the stock GM springs. I'm not ready to take the $1000 gamble. If it gets to that point I'll probably reinvent things and go longer wheel base, linked, maybe coilovers, etc. I'm happy at this point and that project is a long way off.


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[Jesus_man]

Ahh, so leaving the front spring hanger where it's at, means 54-48 = 6". Divided in half, carry the one, square root etc... that would push the rear axle back 3" from stock. Which is where I think I want to be eventually. Are we talking stock GM Springs here or lift springs? And if stock, what lift are you gaining from them?

Your axle is 4" back from stock, then how far is center of axle from...say the tail light?

[Gunnibronco]

I bought stock junk yard springs that were fairly high mileage. My goal was to set them for a 3.5” lift.

Unfortunately I mismeasured something and had to add a 1” lift block. It's not easy to tack everything together and know where you'll end up once all the weight is in the truck.

With the shackle under the hanger I could have used a 2” longer shackle but it changes how the springs flex/cycle and I felt it was going to leave me with a stiffer set up and more likely to invert the springs. So I went with the lift block. Fortunately I haven't seen any negative results of the block. I could have chopped every thing off and reset it all, but that would suck so I went the easy route and hoped for the best.

I'll have to measure where the axle is compared to the lens.

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[Gunnibronco]

So somehow my response to your question on the DOM radius arm thread ended up on a post above. I've moved it over to the right thread. It's probably my fat fingers on the phone, I really prefer the laptop.

I just noticed your first post mentioned the fuel tank. I'm running a 20 gallon Aero tank moved back a couple inches right to my rear bumper. With this and the 4" I think I moved the axles, I could still go back one inch. I tried it but the tire flexed into the fuel filler neck I built. The only way I could see avoiding that is to move the fuel tank into the bed or come up with a filler neck that goes into the cab, or limit up travel quite a bit. I don't think you'll need a design for a fuel tank if you move it back. Of course I'm on wide axles so you might see something different with stock width.

I'll take some measurements and pictures of where everything sits.

[Gunnibronco]

I took some measurements from my 74 and my 72 for reference.

Highly Frankensteined 74:
Center of axle to quarter panel/tail light body seam:20-1/4"
Center of axle to door opening:30-9/16"

DSCN8599.JPG

DSCN8600.JPG

DSCN8601.JPG

72 with old 70's or 80's lift (no guarantee this represents a "stock" axle location).
Center of axle to quarter panel/tail light body seam:25-3/8"
Center of axle to door opening:25-1/4"

I did take these measurements on both the driver and passenger sides of both trucks and they matched within about 1/16"-1/8". So nothing is super out of whack on either truck.

Since taking measurements from the body isn't really accurate, I took measurements (as best I could-it was hard without pulling a tire off the 72) from a hole in the frame on the passenger side.

DSCN8602.JPG

This also showed a 5" difference. So......?

This seems like my 74's axle is 5" further back than the 72's axle. This is surprising and probably NOT 5" from stock. My wheel base is 97.25" which is 5.75" longer than stock, I know my front is almost 2" forward from stock as well, so this points to my rear being about 4" further back from stock. My guess is the old lift kit has pulled the axle forward on the 72. I think I've read this is before as well.

Admittedly I did not take any measurements before cutting everything off the 74. Shame on me.

Also, with a decent amount of weight (tools, parts, Hi-Lift, gas, spare tire, bumper, hard top, etc). I measured 8-5/8" from the top of the axle to the bottom of the frame. So not quite 3.5" lift by most standards. More like 2.5"-2.75" lift.

On an early test drive, I put the axle 1" back on the spring perches. I was rubbing the tire on my "custom" filler neck without a lot of up travel. It did not hit the gas tank. I moved the axle back to centered on the spring perches and I don't seem to be rubbing anymore. I should repaint the filler neck and check. You can see the clean mark on the filler neck in the picture below.

DSCN8603.JPG

[Jesus_man]

Thanks so much for the measurements! In my initial plan of pushing the spring hangers up 2" and back 3-4", I was planning to regain the height using Spring Rockers which adds 2" of lift. I used them on my other bronco before it got totaled and they worked great. So, with the stock GM springs giving 2.5" of lift, and moving the spring hangers up 2", there would be very little lift. Then I add 2" for spring rockers, and I still need to come up with about an inch of lift ideally not using blocks. Just thinking out loud here. That may be more effort then cutting off what I have and moving the entire assembly. And again, I am fairly happy with these springs other than the axle wrap, which I already have most of the parts to negate. It's frustrating that my bronco isn't just down in the garage to go compare measurements.

Really, the body work is what has me at a hard stop on pushing the rear axle back. That and dealing with the filler neck...

I have spoken to Aero Tanks and sent them a custom designed tank they said they'd build for what I remember being a reasonable price. What I had planned to do is shorten the overall height of the tank and make accommodations to push it as near to the body as I could. Then I was going to have them take out of semi-circle right where the pumpkin is located that would allow me to run this tank under the bed and still push the axle back. While I am building a custom tank, there would be an option to move the filler neck to an entirely new location. Maybe even to the front tank hole and route the filler to the front drivers side of the tank? That could make for some interesting bending, I think it could be done easy enough.

[Gunnibronco]

The complicated part of the GM spring swap was figuring out where the springs need to be hung (height and distance between hangers), and shackle length. There are no reference points for any of these measurements. Both the stock Bronco and GM springs are shackle over the hanger and I swapped to a shackle under. So it's all new and somewhat guestimated. You can't really fully load the suspension with weight if everything is just tacked in place. And once it's all welded, it's too late for easy adjustments. It's not a straight forward swap. I wasn't really expecting it to be as complicated as it turned out.

I don't know if newer springs would gain what I'm missing. Or rearching my springs. Or new custom springs. Or cutting the hangers off and repositioning them.

At this point I've worked out the bugs and everything is ok. Not exactly to plan but it's up and running well. So I'm putting these issues on the back burner for now.

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[Jesus_man]

Understood. It's a bit of trial and error, but once you weld it down, it's not fun to pull it back off.

For clearance reasons, I think I still want to stay with shackle over as, so then I am really back to the drawing board if I would decide to run a different type of spring. Just a quick search yielded that most lift kits for this genre of Chev use blocks for the rear. BDS has a $583 adder if you want full spring packs, but this was for a 1500 pickup, which is likely NOT the same spring rate as our broncos. So that becomes a bit of a mess for me.

[Eck]

Understood. It's a bit of trial and error, but once you weld it down, it's not fun to pull it back off.

For clearance reasons, I think I still want to stay with shackle over as, so then I am really back to the drawing board if I would decide to run a different type of spring. Just a quick search yielded that most lift kits for this genre of Chev use blocks for the rear. BDS has a $583 adder if you want full spring packs, but this was for a 1500 pickup, which is likely NOT the same spring rate as our broncos. So that becomes a bit of a mess for me.

What do you expect from a Chevy? Maybe you could try some Nissan springs

[Gunnibronco]

I haven't found anyone building a lifted spring for these trucks. I think it would take a call to Alcan or Deaver to get a good quality lifted spring pack. For the price I'd probably start seriously considering a 4 link.

Here is the spring rate/size chart that sent me down this path.
99-05 Tahoe/Yukon/Denali/Escalade

[Jesus_man]

For the price I'd probably start seriously considering a 4 link.

Indeed. If I am getting above $1000 for rear suspension, I don't think I'd be sticking with leaf springs.

Thanks for the spring specs. Would love to know if there is a library that has more vehicles.

[dbasile]

I thought about linking mine too. But I am cheap. 3rd place on the rti at Super Celebration West in the extended wheel base class with leaf springs.

I got the leafs from a 99 escalade. The big deal is 5 1/2 front springs with a little less that 4 inches of lift. I moved the rear back qbout 4 inches and am just shy of hitting the crossmember or the fuel tank.

Prior to my changes I too had terrible rear wheel hop. Gone now. I also installed bigger spring perches, this may have helped.

That's awesome. 3rd place in a class that probably included some linked/coilover rigs.

I'm not sure but our trucks are the only ones I know of running the 54" GM rear springs. Seems like we stumbled on a pretty nice combo.

How did you decide to go this route? It was kind of a whim for me. I saw a chart with a bunch of spring specs and these matched weight ratings with EBs and the dimensions put the axle where I wanted it.

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I used to have a Toyota, the rear end articulation was not good. The big deal with the Toyota community was swapping 63" chevy springs. I started looking at options on how to get a longer spring under the Bronco. I saw the same chart you post later in the thread. I was torn between the yukon/escalade spring and running the f150 backwards (read a lot about this one and saw a rig in person). If I did it all over again, I would probably go with the f150 (2wd) spring. There would be 2" less spring sitting behind the axle.

I also knew a limiting feature of the bronco suspension was the short shackles. Shackle length effects spring movement so I wanted to go with a longer shackle flip or not I did not care. It turned out way easier to flip it.

After I found some yukon/escalade springs in the wrecking yard for like $75 then I saw your thread. I am surprised there are more out there running these springs or even the backwards f150s. The extra length equals great articulation. When I built mine, I was shooting for about 3-4 inches of lift closer to 3 was preferred but ended closer to 4. I used the adjustable spring buckets up front to match it.

The spring rate of the yukon/escalade spring seems softer. I am level and good with people, tools and a spare with the bikini top, once I put on the hard top for cooler temps, the rear squats.

I think a lot of what helped the rear hop were the longer spring perches on the axle. If I stayed with the early bronco axle I probably wouldn't have messed with the perches. But I went to full widths so I felt I needed to move them.

[Jesus_man]

I would love to see a side picture of your rear shackles. The only reason I am leaning away from a shackle flip is departure.

I've wheeled with enough leaf sprung YJ's et al, and have seen the issue when you're trying to climb something and you can't even get a tire onto it because the shackle sticks further out than the tire. And I am just afraid that I could get myself stuck between a rock and hard place where I can't back out of an obstacle because the rear shackles are dug into a rock or something.

But I certainly see the appeal and the logic is there for better flex and control.

[Gunnibronco]

I'd like to see pics of your springs/hangers/shackles as well. All this talk has me thinking about cutting mine off and lowering them and inch or two to get to where I wanted to be (3.5"). It would gain me some up travel as well. My shackles are 5" long and do hang just lower than the bumper/gas tank. That would be my main concern as well. I'll take some pics and post them.

I saw the video below after I did everything. My 5" shackles did not move as much as I'd expected so I played with a 3.5" shackle. Using the equation in the video, 3.5" is where I should be. The shackle moves/swings much further than my 5" shackle. It felt like the rear would be VERY soft, the rear suspension moved very easily compared with the 5" shackles. It also did not increase, or decrease the overall travel noticeably. I did not run the 3.5" shackle, I only experimented with it before my rig was running. Because it further lowered the back of my truck I stayed with 5" shackles. A longer shackle was getting closer to 6 o'clock, and I was worried about the spring inverting on long droop, so I added a lift block to get closer to the 3.5" lift I was hoping for.

https://www.youtube.com/watch?v=BhqZkF2D6ss

[Jesus_man]

That's a great video. I wish he would have done with with our stock Tension Style Shackles.

[Gunnibronco]

That's a great video. I wish he would have done with with our stock Tension Style Shackles.

You could not get enough lift from the flat spring without installing the hangers below the frame with a tension type set up. It will take an arched spring.

In some ways building a linked set up is more predictable than swapping leaf springs to another make/model. There were way more variables than I imagined when I started this.

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