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Classic Performance Products |
Installing a Rear Leaf Spring Conversion Kit
in a 1955-59 Chevy and GMC |
By Jim Aust |
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In last month's issue of Custom Classic Trucks, we
showed you the first half of dropping a '55-59 GM pickup ("Drop, Stop
and Go!" Apr. '06) using parts from Classic Performance Products (CPP).
In this issue we follow along as one of CPP's '55-59 GM pickup Rear Leaf
Spring Conversion Kits is installed in a '56 Chevy half-ton pickup. The
kit lowers your pickup's rear 3 to 4 inches by placing the rearend on top
of the leaf springs. Just moving the rearend to the top of your original
springs will actually place it too close to the rear rails and won't allow
it to travel more than a couple of inches (maybe less depending on the springs'
condition) before it makes unwanted contact with the frame. |
CPP's Rear Leaf Spring Conversion Kit lowers your truck's
rear and gives it plenty of room for travel, and it's equipped with the
necessary hardware to update your rearend to a later model unit with larger-diameter
axle tubes. The kit features brand-new dropped leaf springs, a shock kit,
brackets, shackles, hangers, U-bolts and mounting instructions. Since the
front of this truck was previously upgraded to five-lug disc brakes, it
was natural to convert the rear to a later-model rearend with the same GM
4-inch bolt circle. |
We used a GM 10-bolt rearend from a 1981 Pontiac Trans Am
equipped with the desirable Posi-traction and disc brake options. Our rearend's
width perfectly matched the original unit's, with 62 inches measured from
wheel mounting surface to wheel mounting surface. Once the rearend was buttoned
in place, the final touch was a fresh set of rolling stock from Wheel Vintiques
and Coker Tire to match the front rollers. Get your own ride looking and
riding better than ever with pieces from Classic Performance Products. |
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CPP strongly recommends removing the truck bed because it
makes it much easier and safer to complete the installation. This also made
for a great opportunity to fully inspect the vehicle's rear and clean up
the frame as necessary. Most everything in this picture will be discarded,
except the perimeter frame. |
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With the original rearend removed and out of the way, the
old leaf springs and mounting brackets will be added to the scrap pile. |
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The easiest way to remove the leaf spring brackets is to grind
away all the out- side facing heads of the rivets holding the bracket to
the frame. |
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After removing the rivet heads, we cut through the upper corners
of the brackets and knocked them away with a small chisel. |
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With the upper corners no longer holding the brackets to the
frame, we used a large chisel to free the bracket entirely. The remnants
of the rivets were knocked through and free of the frame with a center punch. |
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Removing the upper shock brackets required grinding off the
rivet heads securing them to the crossmember. |
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After grinding away the rivet head, we marked the rivet's
flush side with a center punch. |
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We ran a drill through the rivet to relieve its mechanical
pressure. We can now push the rivet out the bracket and crossmember. |
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The clean rear rails are now ready for the new parts. This
is a very good time to restore the rear frame and clean away decades of
road debris and rust. |
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The new leaf spring brackefs are installed in the same manner
as the old using the original upper two holes as a reference. Secure the
bracket to the frame with the supplied hardware. |
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With the bracket in place, drill the remaining holes in the
bracket through the frame with a 3/8-inch drill bit and fully secure the
new brackets to the frame with the supplied hardware. Repeat this process
with all four brackets, including the rear shackle mounts. |
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The new upper shock brackets mount outboard of the original
upper bracket hole. Measure over 3-1/2 inches and down 1-1/8 inches from
the crossmember's upper edge. Mark this spot and dimple it with a center
punch. |
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After drilling the marked spot with a 7/16-inch drill bit,
mount the upper bracket and shock with the supplied hardware. |
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With the bracket secure, drill the two remaining lower holes
with a 3/8-inch drill bit and finish securing the bracket with the supplied
hardware. |
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After installing all the new mounting brackets, it is time
to mount the leaf springs and hang the rearend. |
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The new leaf springs bolt right into the new brackets with
the heavy-duty supplied hardware. |
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The new rearend can be rolled into place on a floor jack and
the leaf springs lifted into place and secured to the rear shackle brackets.
With the rearend resting loosely in the new axle pads, support the rearend's
nose until it's firmly tightened in place. |
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Tighten the shackle pins in the dog-bone brackets using the
supplied nylox nuts. |
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With the rearend centered correctly on the axle pads, secure
the rearend to the leaf springs with the U-bolts and the five-hole lower
mounting plates. At this point, check the pinion angle for three degrees
up from ground level. |
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The shocks can now be mounted to the lower five-hole bracket
that also doubles as a shock mount. |
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With all the pieces in place and the rearend sitting on the
wheels, the pinion angle can again be checked with a dial indicator. Optimally,
all the vehicle's weight should be in place and the pinion angle checked
one last time before welding the axle mounting pads to the rearend housing. |
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The finished installation is ready for the new driveshaft
to be measured. Then the bed can be returned to its rightful place atop
the frame rails. |
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Because we swapped from a six to a five-lug passenger-car
bolt pattern, fresh rollers are definitely in order. We achieved a super-cool
retro look with a pair of beautiful chrome-reversed wheels from Wheel Vintiques
wrapped in a pair of U.S. Royal wide whites from Coker Tire. A timeless
look never goes out of style! Not quite ready for its debut, the truck is
moving along through its rebuild nicely thanks to easy-to-use products from
Classic Performance Products. |
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It's always best to have shop and assembly manuals on hand
to make sure your installation is correct and to make the project as easy
as possible. We recommend factory manuals, available at Greg's
Automotive |
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