2 Big Broncos 4x4 Technical White Papers
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Take this information for "face value" and use with your own discretion and wisdom.
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.
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.
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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