2 Big Broncos 4x4 Technical White Papers

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Description and Reasoning

Upon request, here is the write-up on how I inverted the shackle and subsequently lifted the rear of my Bronco utilizing front spring brackets. My current setup includes a Ford 10.25, two inch blocks, and the shackle inversion. This configuration gave me right at about seven inches of lift. Subtracting the two-inch blocks and the somewhat negligible lift associated with the larger diameter axle tubes (about 3/8 of an inch) the inversion alone was responsible for five inches of lift. Additionally, I left out the stock angled shims because lifting the truck via shackle inversion creates (in my opinion) the positive effect of shifting the pinion angle up towards the transfer case. Even with the seven inches of lift, the pinion on my 10.25 points almost directly at the transfer case output.

The basic premise of the shackle inversion is that you use a set of the forward-most rear leaf spring brackets from the rear of a Ford truck and use those to replace the current shackle brackets.This causes the leaf spring to be underneath and lower than the shackle, whereas the stock configuration has the leaf-spring above the shackle. Essentially you're converting the factory "tension" shackle setup into a "compression" shackle setup .

Locate The Parts

The first step was to purchase the new brackets from a local junkyard. Any Ford truck should have the required brackets. Make sure the new brackets are the same as your present brackets in regard to how far away from the frame the center of the leaf spring is. I'm tempted to say that all Ford trucks have this same measurement, but I could be wrong. I was lucky enough to happen upon a mid-'80s F-250 that had the front brackets bolted on instead of riveted on. Chances are however, that you will have to remove rivets in order to get yourself a set of these brackets. Aside from the rivets, plan on needing to use a lot of motivation to remove the leaf springs from the brackets. You might be able to just unbolt the two, but I used an oxygen/acetylene torch and cut the bushing and bolt off. The junkyard charged me twenty dollars.

Setup

After obtaining the new brackets, it was time to start the work on my Bronco. Of course make sure to have the vehicle properly supported on jackstands before you start this process. I had decent luck with the jackstands supporting the frame just aft of the transfer case. I also stacked a few old tires between the ground and the gas tank skidplate just in case the jackstands decided to give way.

The Time Required

I spent about ten hours doing the inversion.

The Work Required

First, I needed to remove the shackles from the shackle brackets. I figured it would be easy enough to unbolt the two, but I was mistaken. The bolts on both sides of the Bronco were rust-welded enough to where they both broke while trying to turn them. Since I didn't have much other option, I had to use the torch and cut the two apart. I was able to do so without destroying either the shackle or the bracket, but I had to torch out the rubber bushing to get to the broken bolt. I figured it would be easy to find a replacement bushing for the shackle, but I was wrong. None of the parts houses had anything and so I went to Ford. There I learned that the bushing comes as part of the shackle and that Ford could sell me two new shackles for about a hundred and twenty bucks. In desperation, I called a friend who worked at a local 4x4 shop and he was able to have them press in poly bushings. I think he mentioned that the bushings he used were made for a Wrangler. But you will be best off if you can just unbolt the shackle from the bracket. I would suggest using lots of penetrating lube.

The next step was to remove the old shackle brackets from my Bronco. The rivets on these brackets were fairly accessible and so it wasn't too difficult to remove them. I was hesitant to use the torch since it was so near the gas tank, so I ground off the rivet heads and then pounded them out.

View of the rear shackle prior to removal.

At this point, you're pretty much ready to attach the new brackets. Their orientation is the same as they used to be on the donor truck, but you'll have to figure out where exactly to mount them. Ideally you want the shackle and top of the leaf spring to form an angle somewhere between about 45 and 60 degrees (when the weight of the truck is resting on them). This allows for the most articulation and prevents the shackle from swinging back the wrong way after it's fully extended. None of the existing bolt holes lined up between the old brackets and new brackets. However there is an easy method to align them similar to how I aligned mine. The pivot point of the new shackle bracket lines up directly below the two forward-most holes from the old brackets.

The new location for the shackle mount

As far as actually mounting them, mine are stitch welded to the frame and then the holes for two bolts per bracket were drilled through the frame. So I have two bolts per bracket and inch-long welds along the circumference of the brackets. I'm not sure if welding is the preferred method, but it was the quickest method available and I was in a time crunch with the BroncoFest 2000 coming up soon.

After mounting the brackets, simply reattach the shackles and leaf springs. Overall, it's not a difficult procedure, but it just takes some hard work and time.

The Results

Since doing the procedure I've driven the Bronco for about 1,600 miles. I have no noticeable driveline vibrations, even up to 80 miles per hour. The one minor problem I encountered was that the rear was able to articulate enough to where the CV joint maxed out to the point of ripping one of the zerk fittings off of itself. I was able to simply replace the zerks with the kind that require a little needle attachment thing on the grease gun.

Otherwise, I have nothing but good things to say for the inversion. All told I spent basically only $20 for the entire thing (granted I did all the labor/welding myself). Any questions, just ask....

Chris Gzybowski - gzyboc@rpi.edu
1988 XLT Bronco

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