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The Jeep: Suspension
(Last Update: 3 March 2003)
Current Statistics:
Initially, I got a great deal on a complete Superlift 2" setup. I actually bought it before
I had axles. (I was going to go mild on the suspension. That idea sure didn't last long.)
The kit included all four CJ springs, yellow polyurethane spring bushings and shock bushings,
U-bolts, shocks, and shock boots of my choice of colors. It wasn't long before I was thinking
of going spring-over, even with the lift springs. Then, after purchasing the front axle and
the first rear axle, I started a session with the tape measure. (To see what happened with
the first rear axle, please go here: The Jeep's Axles.)
Oops.
The front axle I bought wouldn't fit correctly with front leaf springs. The driver's side
spring would end up entirely on the cast differential housing, since I'm using full-sized
truck axles, instead of shorter Jeep axles. The fitment wouldn't have been a problem if I
was using a YJ frame, as those are 5" wider between the front rails than a CJ-7 frame.
(With lessons learned on this project, I'd use a YJ body with the CJ hood and grille and a YJ
frame if I were to do this over again.) I looked at outboarding the front springs. Looked at
it really hard. I'm not the world's greatest welder, so welding up the brackets scared me a
bit. I looked at using ones just like on the Bronco I had (the rear springs are outboarded
from the factory), but at $44 each from the dealer, and $45 each from the junkyards (they're
held on by 2 bolts and 2 rivets, so the yard would have to cut 'em off for me), plus the fact
that the position of the spring would be kinda high on the frame, I was looking at other options.
As previously mentioned, while cruising the junkyards one day looking for disk brake parts, I'd
found the frame of a 1979 Bronco on top of a van. Well, the suspension on it was still on my
mind. After a few discussions with some friends of mine, Chris and Lars, as well as Dad (one
of the original Jeepers in this world, and a darned good mechanic) I went back to that yard to
find the Bronco frame still sitting there as I'd first seen it, except that some overheated
Northwester had pulled the front brakes and steering knuckles off of it. The suspension was
intact, but the springs were shot. One looked like a bent slinky, and the other had about a
dozen of those screw-in coil spacer thingies that you find in the scary aisle of the parts
store. That's fine, as my folks had a 1979 Bronco, and those puppies were HEAVY, thus making
those springs no good for my use even if they weren't sprung. (Or is the word "sproinged"?)
I went back on two consecutive days (there's one of those repeated themes of mine again) and
got the suspension. It's all a bolt-and-nut affair (no rivets), which made it fairly easy
to disassemble.
Side note: Something surprising to me was the fact that the 1979 control arms are a
full 10" longer than the ones on my 1984 Bronco with the Twin Traction Beam front suspension.
No wonder a lot of lift kits for the TTB include longer arms.
Another side note: An advantage to a coil spring/control arm suspension on an
off-road vehicle is that if the vehicle pulls up to something that will clear under the
bumper, such as a log or ledge, the first part of the vehicle that hits is tire, not leaf
spring or spring shackle.
Mounting the Bronco suspension took a bit of work. The 1985 Jeep frame is 36" wide (center
of the frame rail to center of the rail) at the rear, and 26" at the front. The transition
between widths is between the fixed spring mounts (in reference to the body, the frame flares
in the area under where the driver sits). Except for a couple-few inches between the front
bumper and the front crossmember, the frame is fully boxed. Where the control arm bracket
needs to mount, the inside of the frame rails are parallel, but the outside is just starting
its outward bend, so it's angling out towards the rear. The Bronco frame rails are parallel
for their entire length. It's modification time.
I only needed to make the outside of the frame rails parallel; the inside of the rails were
already parallel in this area (it's not really necessary for the inside of the rails to be
parallel, I guess, but it makes bolting on the brackets a whole lot easier if they are). Using
some 2"x2" lumber and every clamp I had, I mocked up where the suspension arms and brackets
needed to go. I found that the brackets needed to go right behind the mounts for the front
corners of the body tub, and that would still leave me enough room to move the axle forward a
couple of inches. Coolness. With that positioning, I need a 13/16" spacer under the front of
the plate that I wanted to use for the outside of the frame rail. Gee, if I lay a piece of
1-1/4" angle iron with both edges touching the frame rail, a quick touch of a grinder against
the corner that juts out gives me my 13/16". (Hey, all that high school math finally came in
handy!) I welded the angle iron on, bent a plate to so that it has about a 4" run along the
frame rail from where it touches in back, and fishmouthed the rear end of it before welding
it to the frame and the angle iron (everyone that I feel knows anything about frames recommends
the fishmouthing whenever you can do it). I then welded plates on the top and bottom of this
plate, to make a full box. The back ends of these plates do not extend as far back as the
side plate, to keep all the stresses spread out. (If this doesn't make a whole lot of sense,
go here for pictures:
Front Suspension Mount Pictures).
After all that, I drilled the holes thru the frame (and thru my new work) for the 1/2" grade 8
bolts I'm using to hold the control arm brackets on. Each bracket has two horizontal holes and
two vertical holes. The frontmost of the horizontal holes goes right thru the angle iron. This
was not fun to drill, and I destroyed four small drill bits (drilling pilot holes), ripped the
end off of a 1/2" bit, and then bent a brand-new 1/2" bit and an 11/16" bit.
I started this whole process by clamping the brackets in place and measure everything about
17 times. I then put the 1/2" bit into each of the bracket holes and triggered the drill just
enough to leave a nice dimple on the frame rail right in the middle of where I needed the
holes. Then, I used (for starters) a 1/8" bit to drill a pilot hole thru. After using a few
other small bits, since I broke the 1/8" bit on the angle iron, I had my pilot holes. I then
removed the brackets and drilled everything out with a 1/2" bit.
Since just putting the bolts in and cranking 'em down would pinch the frame rails, I needed to
put in some spacers. I couldn't find any spacers long enough for what I wanted to do, so I went
to the plumbing section of the home improvement place and got some short lengths of 3/8" pipe.
* Note: Pipe sizes are based off of the old lead pipe sizing standards. For a given
"inside diameter" (the size talked about), the outside diameter will be the same, but the inside
may not be. In other words, 3/8" internal diameter lead pipe had an outside diameter of
11/16". Iron is a stronger material than lead, so the iron pipe has a thinner wall than the
lead pipe, but still has the same outside diameter. Steel is even stronger, so it has even a
thinner wall, which yields and even larger inside diameter. The reason the outside measurement
stays the same is so that you can use the same screw-on fittings for all pipe that claims to be,
in this case, 3/8".
The pipe that I bought has a 1/2" inside diameter; perfect for 1/2" bolts. (I picked it out
because of the 1/2" inside measurement. It just so happened that the outside diameter is 11/16",
which is called 3/8" pipe per the lead pipe standard.) I cut the pipe into sections about 1/4"
longer than I needed, ground one end flat and square, then ran a 1/2" drill bit thru the small
pieces of pipe to clean out the welding spur inside the pipe so that the bolts would pass thru.
That's right, the pipe I bought is welded tube, so it had a line of welding spur down the length
of the inside.
The next step was to use the 11/16" drill bit and re-drill almost all the holes. I drilled
the ones on the bottom of the frame rails, but left alone their partners on the top of the frame
rails. I then drilled the horizontal holes, thru all the various layers of metal, leaving the
ones on the inside surface of the frame rails alone. The reason for leaving the surface of the
frame furthest from the bracket, is so that the spacer will be clamped between the bracket and
the frame, and thus can't slide out the other side if the frame gets compressed at all.
* Note: When drilling this setup, remember that the center line of the drill is going
square thru the outer plate and the frame rail, but is at a 45-degree angle to the surface of
the angle iron. In other words, BE CAREFUL. I've yet to see a drill bit with an angle on
the end that is steeper than 45 degrees; they're all quite a bit less than 45 degrees (actually,
according to my junior high shop teacher, most are 23 degrees). What this means is that the edge
of the drill bit is going to start cutting before the center of the bit makes contact with the
metal. Go slowly, use a light touch, and get a good grip on the drill with both hands.
As in the text above, I bent a very large drill bit while drilling these holes. If you don't
have a really good hold on the drill, you can get hurt when the bit binds.
Now that I had all the holes drilled, I put the spacers in (nice end in), tapped 'em all the
way in with a hammer, then used the small hand grinder to make 'em flush with the frame rail.
This way, each spacer perfectly fits its location. (If I ever find myself taking this thing
apart, I'll have to remember to mark the spacers, so I put them back in the exact same places.)
I then bolted everything together, using big flat washers under both the bolt heads and the
nuts.
I had to weld the C-brackets back onto the front axle, but I didn't feel too bad 'bout
having taken them off for the original suspension plan, since they had to go on closer to the
middle of the axle anyway to make up for the narrower CJ frame. (I would not have had to move
them if I'd been using a YJ frame.) I put the front axle in, with the brackets just being
pinched in the suspension arms and the C-bushings. (C-bushings are the rubber, or in my case,
polyurethane pieces that fit around the axle brackets adn are then clamped inside the end of
the radius arms.) I then did a lot of tapping with a hammer and checking with an angle finder
to get the caster angle set to where I thought I wanted it. I then let it set for awhile,
checking the angles a few days later. (I find I do better if I measure up something, leave it
alone for a few days, then go back and check my measurements again later, when a friend is
looking over my shoulder.) I put a quick tack weld on each of the brackets to hold them in
place on the axle tube, then I pulled the axle and finished the welding. After everything cooled
down, it was time for some more Hammerite paint.
While all this was going on, I had the rear axle housing sitting across the rear springs, just
to get an overall look at things while working on the front axle housing. I'm gonna need some
major fender flares, 'cause this thing is gonna be wide...
Oh, if you're wondering; the front fender still fits just fine, as the spring tower bends
outwards a little bit just above where it mounts to the frame rail. Also, if you've noticed,
I'm using all 1/2" bolts. Not only are the 1/2" bolts stronger than the stock stuff because
of its larger size, having all of the bolts the same size allows an amount of interchangeability.
In other words, I can carry a set of various length 1/2" bolts in my on-board parts kit, and
be able to replace pretty much any bolt that should happen to break.
The F-100 springs are temporary. They're a couple of inches short right now as things
stand, and that's without the weight of the front sheetmetal, engine, or other underhood
components. I'm looking at using a set of early Bronco lift springs, as that's a comparable
vehicle as far as weight, and they'll fit the suspension mounts perfectly.
The next things I needed to start on was the track bar setup and the shock mounts.
The right-hand suspension arm had a lower shock mount ready to go. It's basically two
bent plates that are riveted thru two holes in the arm, right behind the axle. (You can
see this is the last of the pictures above.) The left arm had the two holes, but no plates.
Instead, the shock originally bolted to a projection on the front of the cap piece of the
arm, so it was in front of the axle. Since that projection gets in the way of how I'm
setting up the tie rod (and since I thought it looks funny having on shock in front of the
axle and one behind), I cut off the projection and ground it smooth. I then bent some
pieces of plate steel into brackets, matching the ones on the right suspension arm as
closely as I could. Since I don't have a way to rivet the plates on, I bolted them on with
some 7/16" grade 8 bolts and nuts.
I looked at using the factory shock towers in a relocated position, but since Jeep put the
factory lower shock mounts so low on the axle, the stock towers aren't nearly tall enough.
Instead, I bought some front shock towers meant for a 1986-1996 (and maybe even later)
Ford F-250 or F-350 truck. At $13.02 each, I was more than willing to buy nice, new,
un-rusty ones than spend $10-$15 each plus gas and time at the junkyards for rusty used
ones. When I first held these mounts up to the frame, the length on them was perfect.
I put the shock mounts one inch behind the spring towers, with the bottoms of both towers
even with each other. Alignment was easy; I put a 1" wide block of wood between the spring
tower and the shock tower, then clamped everything in place. Once again, I found myself
drilling the frame for bolts. This time, I only drilled two 1/2" holes thru both sides of
the boxed frame. A factory hole in the frame rail was close enough that I could use it to
put in some tube spacers to keep the 1/2", grade-8 bolts from crushing the frame when I
tightened 'em down. Then, all I had to do was to bolt up the shocks.
(For the part number on the shock towers, check here: Part Numbers.)
The track bar is going to take more work than the shocks. Leaf spring suspensions can
live without a track bar (often called a panhard rod), but coil setups requre a track bar
or some other kind of triangulation (such as A-arms or a triangular link). Without the
track bar, the front end of the Jeep will slide off kinda sideways, even if it's sitting
still, and would be totally uncontrollable to drive. The track bar that came with the front
axle is about a foot too long.
Here's a bit of theory: Ideally, the track bar should be as long as possible, and should be
the same length as the steering draglink, as well as being exactly parallel to the draglink.
This eliminates as much bump steer as possible.
When I say "parallel" here, I'm talking about an imaginary line that runs from the center
of one end of the link to the other. (If the link bar is perfectly straight, then this line
would be running right thru the centerline of the bar.) So, really, I'm talking about
parallel between this imaginary line on the draglink and the same kind of imaginary line on
the trackbar. The "length" would be the measurement along these imaginary lines from pivot
point to pivot point. The reason I bring this up, is that a lot of track bars have a bend
in them, so that they clear oil pans or differentials. Also, there's a lot of extremely bent
draglinks (the "Z-Link" is a popular one). Many companies make the bogus claim that these
track bars eliminate bump steer. Really, all a bent draglink does is clear stuff under the
truck, like the oil pan or suspension pieces. Installing a bent track bar does not change
the location of the pivot points, and thus has the same resulting geometry as a straight
track bar; it has no effect on bump steer at all.
I found a 1966 Bronco (the early style) in the same junkyard that I purchased the axles from
last summer. I'd already pulled the transfer case out of this Bronco on an earlier trip, and
on my second trip, I pulled the driveshafts and the track bar, the latter of which appears to
be just the right length for my Jeep. I had originally thought about using the track bar
that came with the front axle, but $10 for the early Bronco track bar was less than I'd spend
on having the long one shortened. The rubber bushings in the Bronco trackbar are shot (I can't
complain; they were 34 years old). I replaced them with polyurethane, just like I have with
every other piece of suspension rubber.
The axle end of the track bar was the easiest to figure out; I used the heavy cast bracket
that was the original mount for the steering ram. For U-bolts, I used two of the U-bolts that
were provided for holding the axle to my now not-used front leaf springs. These U-bolts are
bent from thicker rod than the originals (as well as being brand-new), so once again, I got
out the big drill and drilled out the holes in the bracket from 5/16" to 3/8". I also had to
drill out the hole for the track bar bolt, as that hole was originally tapered.
The frame bracket for the track bar on the early Bronco that I had pulled the bar from had
been welded onto the frame by some previous owner (as had all the suspension brackets), so I
needed to find an alternative.
The solution came from the same big Bronco frame that I goten the front suspension parts
and axle knuckles from. On the 1978/1979 Broncos, the left front shock tower drops below
the frame rail and is notched and drilled in the extended lower end so that it can also act
as the frame mount for the track bar. I hadn't gotten the shock towers from this frame when
I got the suspension, as they're set up for the kind of shocks that have the threaded pin on
the top end that goes vertically thru the mounts, and because these mounts are a couple of
inches taller than the spring towers as well as leaning outwards a lot. However, this mount
is really thick (7/32" steel) and is forged from one piece. Since the track bar is one of
only three links in this suspension setup, and welds can fail, I liked the idea that it's
not welded from three plates, like most aftermarket mounts are. What I did was cut off the
part of the shock mount that exteneded above the frame rail, and used that scrap to box out
the lower part.
At least, initially.
If you've been following this site for very long, you'll know that at first, I was
planning on using the rear springs from the lift kit that I had purchased in the conventional,
stock, spring-under-axle configuration (typically abbreviated as SUA). The plan was to start
there, then once the Jeep got moving, change it to an SOA (spring-over-axle) later, along with
lifting the front. Well, that changed. I'll explain the new in just a bit; let me go over
how I planned on doing the SUA first.
Beyond that, all I needed to work out for the rear suspension was mounting the shocks.
While my dad was visiting, we took a good look at the rear suspension. The original rear
shocks were mounted inside the frame rail so that there'd be tire clearance in the wheelwell.
This isn't a problem for me, since both my first and second rear axles are at least 6" wider
than the original axle that was in this Jeep. The original frame mounts for the shocks are
only a couple of inches high, and are canted forwards. The original axle mounts hung a couple
of inches below the axle housing. What Dad and I decided would work best is to use the
original front shock towers (about 8" long) in the rear, with the towers extending into the
wheelwell. Then, the axle mounts for the shocks would be welded onto the front of the axle
housing, and thus wouldn't stick down from the axle. Cleaner look, and less likelyhood of
hanging up on something when off-road.
It's a really good point, and has applied to a lot of other things in this Jeep build-up.
Chris backed him up, as did my dad.
Also, at this point, I'd run into the fact that the first axle I had purchased just
wasn't going to work with the front leaf springs. (You can check it out on the
axles page for full info, but basically, all the parts
on it turned out to be garbage.) I purchased another, later version of the Ford 9" axle.
This outside tube diameter on this one measures 3-1/4", instead of 3", like the previous
axle. This means that the U-bolts that came with the suspension kit are too small. By
going SOA, my spring plates aren't usable, as not only are they for a smaller axle
diameter, using them would put the U-bolts pointing down again, which I've been trying
to avoid.
With the SOA configuration, all I needed for each spring plate was a flat metal
plate with five holes drilled in it; four for the U-bolt ends, and one in the middle to
clear the center pin on the spring. (The Dodge spring plates weren't a total write-off;
the U-bolt holes in them were spaced correctly, so I used one as a pattern for drilling
out my new home-made spring plates.)
In preparation for the SOA, I removed the center pins from the springs to turn them the
other way around. The center pins are a high-quality 3/8" bolt with a round head that
bulges in the middle; it looks like a slightly-flattened ball. A plain, old-fashioned
hex nut threads onto the other end of this pin/bolt. However, despite clamping the leaves
of the springs together before removing the pin, I didn't get them out without ripping off
all the threads. No bit deal; I got new ones for less than a buck each at the spring shop.
I also had new U-bolts made up while I was there. Instead of 1/2", I had 5/8" ones made
up for less than a buck more. If you do the math, you'll see that a 5/8" bolt has a cross
section that's 56.25% larger than a 1/2" bolt. That's a lot stronger for very little more
money, and I feel was worth it (but I will agree that it wasn't really necessary). Also,
the nuts that came with these U-bolts are twice as thick and a lot better quality that the
stock stuff, so that weak point has been lessened.
Below is what I started this project with; a piece of 1/4" steel plate and the two
Moroso spring pads.
However, I finally got talked into going spring-over. (Thanks, Lars and Chris.)
The quote from Lars was "Why bother to build something twice?". Chris backed him up.
It's a really good point.
The Dodge spring plates weren't a total write-off; the holes in them were spaced correctly,
so I used one as a pattern for drilling out my new home-made spring plates.
Below, you can see me drilling out a 4"x5" piece of 1/4" steel, to make the U-bolt spring
plate. In the picture, you can see the new plate under the Dodge "template".
Click to see my costs so far.
We'll just have to see what happens. I'll update this page as I figure stuff out/get stuff
done.
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