Digger's '69 Build Thread

[Digger]

Now it was time to slide the front axle under the truck.


Getting things lined up
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I also needed to build some new radius arm brackets, so I started with some flat steel:
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And bent it up with my Redneck press brake:
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Cut and rounded some edges and drilled some holes:
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With the radius arm mounts welded in place I could cycle the axle up and down, checking for clearance issues. First thing I noticed was the tie-rod directly impacting the track bar mount at 5.5" of up-travel.
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The differential and tube barely cleared the oil pan.
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The tie rod and drag link cleared nice, but the mockup track-bar was hitting the diff cover and the passenger-side spring tower at only 4.5" of up-travel. Far short of my 6" up-travel goal.
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[Digger]

So I grumbled and cut off half the old track bar mount and rebuilt it aft 2"
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I didn't get any pictures, but I was having serious heartache over the axle track bar riser my buddy gave me. I just didn't like the single shear design with a 1/4" plate. I spent 3 days worth of spare time at work creating CAD models and testing them in FEA until I had something that was acceptable for the design loads. With that done and built, it was time to paint the axle.
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Close ups of the improved track bar riser:
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While the axle was out, I cut the seam in the passenger-side inner fender, pulled it outward and re-welded it to clear the WH shorty headers. They fit 302's and 289's, but rub slightly with 351W. I had talked to the tech line guy and expected this. The interference was about 1/4", just like they said.
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[Digger]

With all the parts painted, I modified a set of receiver forgings to accept Jeep lower control arm bushings. I chose these because that is where Johnny Joints and other aftermarket joints (including my design) derive their dimensions from. In fact, I only had to clearance an area for the bulge in the bushing.
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The reason I went with bushings in the radius arms was to reduce NVH (Noise, Vibration, Harshness) and provide for some recession damping when the front tires hit bridge seams, pot holes, rocks, etc.
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The last thing to build was a new trackbar that would clear the spring tower and the differential at full stuff. Again, after some CAD modeling and FEA work, I settled on 1.5" x 0.25" wall DOM tubing. I started by putting a 35° bend in one end.
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Then smashing and coping the tube to accept the stock forged end ring.
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I gave the other end the same treatment, but not before breaking my JD2 bending die. It is repairable, but it was a little scary when it let go. Here is the swoopy-cool track bar next to the original ghetto-fabulous unit that I built. I was rather disgusted with myself for getting so far down the path with the attempted straight design. But then I kicked myself in the butt and built a proper unit.
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[Digger]

Finally the moment of truth had arrived. After re-drilling the lower coil seats 1" inboard, I bolted in the coils and to my delight, the ride height came out EXACTLY where I planned it to be. Right now the truck sits 1" higher then the planned ride height of 3.5" over stock, but I am not at the full planned weight of the truck. It still needs cage, bumpers, fluids etc which will bring the weight up and the ride height down, plus get the ride frequency in the correct range.

But for now, I'm stoked about having the wheels back on and being full width in the front.
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[Digger]

Here are some pictures of the links at full stuff. Right now, from the planned ride-height, I have an available 6" of up-travel on the passenger side and 7" on the driver's side. If I wanted to push it, I could trim the right spring tower and have a full 7" of up-travel, but I'm very happy with 6" and it would go a long ways toward a smoother ride while going fast in the rough stuff.


Track bar and bracket at full stuff
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Tight fit, but it all fits!! Notice there is so much up-travel, the drag link is going uphill from the steering box with a stock pitman arm!
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New frame-side track-bar bracket, now aft of the tie rod
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The diff cover, barely clearing the track bar:
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Tomorrow I have a friend coming over to tear up the rear end and strip it clean of axle and brackets. Yesterday my new rear coils arrived, so today I took them to work and verified their rate. Eibach stated ±2% on their coils and they were dead on. This is 4" of compression, the planned sprung weight of the rear
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Not bad. Off to bed now, but more to come!

[D&D72]

Dang you do nice work! how close does does your tie rod come to the track bar riser in full turn?

[Digger]

It touches right as the axle is hitting full lock. Not too excited about it, but it's not hurting anything. It's amazing how tight everything gets on this old beast.

[ZOSO]

how about pics of the fairlane in the back ground?

[Digger]

how about pics of the fairlane in the back ground?

Best readily available pic I have.




The Fairlane belongs to my wife. She helped her dad and brother restore it back in high school.(Mostly paint and interior from sitting for a few decades) When it was finished, it only had 18,000 miles on the clock. Now it sits about 36,000. It's a fun little car for cruising.

[ZOSO]

I love it!!!! Beautiful car.

[Justin]

Its even nicer in person. Both are really sweet rides.

[Digger]

Well I'm back at it. Finally.

After finishing the front it was time to tear apart the rear.
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I had a buddy come over to help for a few hours. We got the axle pulled in no time.
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Then went to work with the plasma cutter and grinders
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[Digger]

With the axle out, I went to work taking measurements and designing the brackets. Since 3.25" hole saws are not common, I used the rotary table to notch the plate to fit the axle housing.
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That was done 3 more times until I had these brackets made. They will serve as the spring mount and long arm attachment to the axle.
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Mocked up on the 9-inch with my first (failed) attempt at a torque arm mount. The mount ultimately failed because it interfered with the exhaust routing. I ended up cutting and grinding it off and moving the torque arm to the other side.
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Modified some more forged receivers to accept compression bushings.
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All the cross axis ball joints and bushings ready to go.
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Next I needed to make a shackle for the torque link. Two more bushings were used on this end to soak up drivetrain shock loads. Jeep lower control arm bushings have a step in the shell to aid assembly. This means I needed to bore two different precision sized holes for each bushing to achieve proper press fit. The great thing about these bushings is they are easy to acquire at any auto parts store. Auto Zone sells genuine Clevite bushings for $7/each, not that nasty Chinese rubber that stinks up the whole garage.
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[Digger]

I didn't take many pictures of the next few steps, but I had to build the frame-side brackets for the long arms and reconstruct the axle-side torque arm brackets. Once that was done, the axle was carefully positioned under the truck and many measurements were taken to square it and place it at proper ride height.

Brackets were then welded into place and links made to connect the two for the first time.
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This is where I got stuck for several weeks trying to figure out the best place for the frame-side torque arm bracket. I could not find a good place where it would not be in the way of pulling the T-case down the road. This meant more brackets and more bolted connections. It also meant to pull the drive train, I would have to pull the torque arm. Not cool. I ended up building a crossmember that goes over the top of the T-case and the shackle hangs down. That provided enough clearance to pull the drivetrain without pulling the torque arm.
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With that in place, I mocked up the torque arm.
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Due to the axle-side joints not sitting directly over top of each other, I placed the shackle saddle off-center to counter the torque-arm's desire to move laterally under load. This should keep the forces in the bushings more square and make them last longer.
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I threw a tire on for effect. It is looking nice with full widths.
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[Gunnibronco]

Wow! I'm thinking about a coil sprung rear end in the next few years. Needless to say, that is impressive. Nice work.

[Jesus_man]

Making good progress! It'll be nice when you're done.

2 comments FWIW, are you going to tie your frame side brackets together. Seems like a good place to get stuck on a rock...
And your torque arm design will work great , but I fear that the bracket under the axle will be a hindrance offroad. Heck, my pumpkin gets in the way all the time!

Did you mention what coils you were using?

[Kinder]

Love the bracketry and I'm inspired by the torque bar setup, I've heard that my pinion is dancing around back there. What type of shock setup are you planning on running?

[Digger]

Making good progress! It'll be nice when you're done.

2 comments FWIW, are you going to tie your frame side brackets together. Seems like a good place to get stuck on a rock...
And your torque arm design will work great , but I fear that the bracket under the axle will be a hindrance offroad. Heck, my pumpkin gets in the way all the time!

Did you mention what coils you were using?

Yes, the more I look at it, the more I want to tie them together. Probably with a plate that will run up the side of the frame.

The pictures are a little deceptive, but the lower, rear bracket for the torque arm placed the joint behind the center section so I could hug it in tighter to the center of the axle and high enough to be nearly flush with the bottom of the diff and still be able to get the bolt in and out. Essentially the bottom of the diff is now 3 inches wider. The torque arm also protects the driveshaft, so I can use it like a ramp to slide over rocks.


The coils are a bit of an experiment. I'm using 3" Eibach coilover coils. By the numbers, they should remain stable and not buckle under full compression. I will position the lower mounts so they angle back slightly at ride height and square the springs more as the suspension compresses. That should help the springs stay stable under heavier loads.

[Digger]

Love the bracketry and I'm inspired by the torque bar setup, I've heard that my pinion is dancing around back there. What type of shock setup are you planning on running?

14" Bilstein 7100s in the front and 12" 7100s in the rear. Both have a custom digressive valve stack that was specifically tuned by my Jeep dynamics buddy for his TJ suspension kit. Being that the geometry and weight of my truck is so similar to that platform, we decided to use it as a starting point to work up my own tune for the Bronco. I'll probably drive it a few months at a time and get a chance to use the suspension in different situations before changing valving.

[Justin]

Question: What's the advantage of having a traction bar that supports the axle above and below rather than a single link to one of those points?

[Digger]

Question: What's the advantage of having a traction bar that supports the axle above and below rather than a single link to one of those points?

It's not necessarily better or worse, but it completely divorces the thrust loads from the torque loads.

Plus I intend to use the torque arm as a driveshaft skid bar.

[Digger]

I'm back with a little more progress. Needless to say, with limited hours and tons of measuring, checking, calculating and double-checking, this rear suspension is taking forever.

With the torque arm and spring brackets on the axle, I needed to create the spring buckets for the frame side. This ended up being a huge task. I wanted to use JounceShocks to supplement the primary suspension so that combined with the generous suspension travel, the truck could really soak up some hits. The JounceShocks work by replacing standard bumpstops with a hydraulic piston that acts as a spring on compression with internally damped rebound. This means that most of the energy produced when you hit the bumpstops is not returned to the system. So when you hit a big whoop or rock, the suspension doesn't try to throw the truck back into the air.

However, since installing these usually implies that a person will be driving the truck harder, I needed to be careful about how they were mounted. To prevent bending the axle, I decided to mount the JounceShocks outboard of the coil springs. Doing this was good for the axle, but bad for the spring buckets because it introduced a lot of bending stress since the JS's were 8" outboard of the frame rails. The end solution was to construct a truss tying the spring buckets together.

I spent a fair amount of time on the computer testing out different styles of trusses and then going home and taking measurements to make sure it all fit. Here is a CAD mockup of the system at max load.

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The top tube actually floats above the bucket and is only tied in at the outboard edge and the inside of the frame rail. The end result prevents the frame rail from twisting off during a big hit.



To construct the spring buckets, I started with the top plate.
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Then bent the side plates with the HillBilly Brake (Patent Pending).
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Welded it all together
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[Digger]

Testing fitting a crusty old JounceShock from work
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Then I proceeded to build the truss. This sucked and was really hard to get at to weld.
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No pictures, but I did put the springs in and put weight on the axle. It was riding high, but the truck is missing 23 gallons of fuel and a 100 lb spare tire, so all was still good. The next headache was the rear track bar. Like the front, I needed to thread the needle with this link. After taking some measurements, it was obvious that building the bracket was not going to be simple. In order to get around all the other brackets and the diff at full jounce, the axle side trackbar bushing needed to be 6" behind axle centerline and 5" above centerline. That is really hanging out there. Frustrated over yet another complex solution brewing, I went back to the computer over several lunch breaks. Only this time, I realized I needed much more of the Bronco in CAD to really know how to build this thing.

Not only did the bracket have to withstand some serious forces (Again, I don't always drive hard, but I want to be able to without breaking.) It had to miss all the existing brackets. Luckily I had already modeled a Bronco frame using some prints I found online. Then I attached my CAD spring buckets and truss. Lastly I needed to build an accurate Ford 9 inch with my brackets on it.
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With those parts in place, I could then model a track bar bracket to get the axle side bushing in position.
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Of course with more CAD models came more FEA to make sure I wasn't going to collapse the bracket. Some tweaks were made, but given lessons learned on the front, but process was faster.
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The time spent CAD modelling paid off big in the garage. Building the bracket went much faster than the other brackets and things lined up exactly how the should have.
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[Digger]

FINALLY with all the link and spring brackets in place, I threw the domed strike targets on the axle for the JounceShocks and tacked them into place. I also ran the axle up to full jounce to check clearances. Everything was tight, which continues to amaze me on a truck this old, but there are lots of tubes and brackets running around. Not to mention all the stuff that is not on the truck, like exhaust and gas tank.
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Here is couple of good shots showing how the trackbar and spring brackets have to miss the upper spring bucket at full stuff.
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The torque arm gloves into the gap in the truss, just as intended. You have to love it when the tape measure doesn't lie.
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Here is the gap I have to shoot through with the exhaust.
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[Digger]

The cold snap we've had brought this project to a screeching halt. Thankfully the weather blessed me for one day and I worked like a mad man pulling the axle, welding, grinding, smoothing, etc. Here you can see the domed targets near the brake drums.
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When the thermometer cleared 60°F, I prepped the axle and started painting.
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Here is good shot showing the internal support on the trackbar mount. That little gusset doubled the overall strength of the bracket.
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After some semi-gloss black / wannabe E-coat paint.
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[Justin]

I have massive CAD skill envy. That's coming along nicely!

[Gunnibronco]

Thanks so much for posting up your process & progress! I'm in awe. This is an awesome thread.

[Kinder]

Very nice! I want to go for a ride when it's done.

[Justin]

You're doing mine next, right?

[Jesus_man]

Yeah, some CAD envy!!

Do what I did with my exhaust, out right in front of the rear tire thru the fender. Loud, a little, but so easy!