Project Mini - Rear Suspension - Part 2
|Author: Jay Kopycinski July 2000
As stated previously, we are building this
truck to have a fairly soft, flexy suspension with 4 to 5 inches of
lift. One option was to purchase aftermarket lift springs, custom
or off-the-shelf. However, to get the lift and flex we wanted
without spending a lot of cash, we chose to assemble our own
hybrid packs, starting with a pair of Mazda 2WD main leaves.
More details on building such hybrids can be found on my
Toyota tech page.
|Starting the rear suspension disassembly
Results may vary when building hybrid springs
and you may have to play with the packs a little to get a combination
that works well for you. Some people prefer not to go through the
possible extra work to build such packs, but you can decide for
yourself. I have found seasoned springs to flex well while maintaining
height, even after being bent backwards repeatedly.
| Setting Up the New Rear Springs
We enlarged the holes in the forward spring
mounts to 5/8" and used 5/8" x 4 1/2" hex bolts and nyloc nuts
to bolt on the forward eye of the Mazda main leaf. We retained
the steel sleeve and stock bushing in the forward end of the spring.
|We built longer shackles for the swap
The plan was to use longer rear shackles, so
we made new ones from 3/8" x 2" flat stock. Center-to-center bolt
hole distance was set to be 7 inches. Poly bushings were used
for the rear hanger and spring eyes. A Toyota application set
was used with 5/8" hex bolts and nyloc nuts. However, the o.d.
of the lower set of bushings had to be reduced to fit in the
Mazda spring eye. Pre-freeezing bushings allows for easy machining
on a lathe using a relatively low turning speed.
We knew that to optimize our shackle angle we
would need to relocate the rear shackle hangers. We used a circular
saw and die grinder to remove the hangers and mounted up just a
main leaf to help set up the hanger location. With the shackle hanger
clamped to the frame rail, we tried several hanger locations. We settled
on moving the hanger 2 1/2" forward of the stock location.
This provides a shackle angle of about 30-35 degrees from vertical with the truck
at rest. With the hanger location finalized, we welded the hangers
back onto the frame.
|Spring hanger clamped onto frame for testing
||Exercising a rear main leaf with a floor jack
||Spring hanger welded at new location
| Building the Hybrid Rear Spring Packs
|Hybrid spring pack mounted
We built five leaf packs using the following
- Main leaf: 0.280" thick, 52" long
- Second leaf: 0.280" thick, 45" long
- Third leaf: 0.280" thick, 38" long
- Fourth leaf: 0.280" thick, 37" long
- Fifth leaf: 0.280" thick, 29" long
| Mounting the Springs and Axle
|Modified axle being mounted
||Plate & bump stop for U-bolt flip
With the springs built, we mounted up the completed
packs. Next, we attached our modified axle housing using an All Pro
u-bolt flip kit. This kit eliminates the use of the stock lower spring
plate and improves ground clearance. Also included in the kit are
new lower shock mounts that can be welded to the axle housing. We
built our own shock mounts so didn't use the All Pro ones. We did,
however, save them for use on our front suspension. To retain the
stock bump stops, we welded them to the top of the All Pro spring
Once the housing was attached to the springs,
we installed the third member, axle shafts, brake parts, and
driveshaft to complete the rear driveline. Our rear driveshaft
was a stock one-piece unit that bolted right back up with no required
If you have a two-piece version, you may want to consider
having a one-piece replacement made. In stock form, the two parts
of a two-piece driveshaft are straight
in line. But, when lift is added, the two parts are no longer in line
and this results in some vibration as the driveline must work through
this angle. The truck may stutter a bit under acceleration and the rubber
in the center bearing will wear quicker.
|Checking articulation and clearance
||Another articulation shot
|Passenger side shock mounted
With the axle in place, we could (almost) install
our shocks. We used 5/8" hex bolts and nyloc nuts on top and the Rancho
supplied self-locking nuts and washers on the lower stud mount. The passenger side shock
bolted right up to our new mounts.The driver side shock has to wait until
our stock exhaust is rerouted up
higher and more towards the driver side. We knew it would be that way.....
| Adding a Two-link Track Bar
The last mod to the rear suspension was to add
a two-link track bar to help control rear axle wrap and pinion angle
while still allowing for full axle articulation.
|Rear end of two-link track bar
||Forward shackle end of bar
I have more detail on building two-link track bars on my
Rear Suspension Tech page. For this bar I decided to make it a bit
more versatile. All three ends are now adjusatable to allow for
any reasonable future suspension changes. The forward rod end is,
of course, threaded and the two rear legs use 3/4" bolt/nut combinations
to allow for adjustment of those ends as well. (Note: one thing not
shown in the photos are the 3/4" jam nuts we added to each leg.)
The front 5/8" rod end is secured to the forward shackle
using a 5/8" hex bolt, tube spacers, and nyloc nut. The rear ends of the track bar use standard
Rancho poly hourglass bushings in salvaged welded-on shock eyes. They are secured
to the rear mount with 1/2" hex bolts in steel sleeves, and nyloc nuts.
The rear suspension came together very well, and all at
reasonable cost. It should flex well with good control, and have
plenty of travel. Overall lift gained from the springs, shackles, block lift,
and moved mount is about 4 1/2 inches. For now we're running a temporary third member.
We'll be upgrading to lower gears and a locker in the near future.
Next month we'll show you the front straight axle swap.
Don't throw away your stock rear suspension parts. We used some of ours on
the front suspension. You might want to as well. Stay tuned as we proceed
Thanks for reading!
- Project Mini - Intro
- Project Mini - Bobbed Bed
- Project Mini - Rear Suspension - Part 1
- Toyota Section
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