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1991 Nissan Hardbody Four-Link Rear Suspension Install - Hittin' Bottom, Part IIGettin' Funky In The Backyard From the December, 2003 issue of Mini Truckin' By Mike Finnegan Photography by Marcel Venable, Mike Finnegan
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Yes, we slacked in bringing you the second part of our Nissan Hardbody airbag install, and for that we apologize. In our defense, we present the final installment of the story, which came out much better for having waited a couple of issues to print. This time around, we'll begin by installing the front Toxic shock absorbers. From there, we'll be installing a complete triangulated four-link rear suspension from Thorbecke Fabrication. The rear suspension will position a pair of Firestone 26C airbags on top of the lower four-link bars, midway between the suspension's pivot points, in a mechanically advantageous design. There are many benefits to this design. First off, this setup takes advantage of the inherent 1.5:1 ratio of the 'bag's design and furthers this ratio by increasing the 'bags leverage. In a nutshell, this type of suspension requires much less air pressure to raise the truck to ride height versus a typical 'bag-over-axle design. The second is that it extends the life of the air suspension accessories, such as the air compressor. As with the first installment of this tech article, we went straight to IMZZ Industries to have the parts from Thorbecke Fabrication expertly installed. You may also notice that our project truck is wearing a new bed. Thanks to the good folks at California Mini Truck Dismantlers, we were spared from having to remove the spray-in bedliner that was already in this truck's original bed. Instead, we found this clean, inexpensive Hardbody bed. We waited to bring this story to you because we found a more efficient way to get a new set of wheels to fit your truck. Boyd Coddington Wheels now offers a service that sends you a blank, unwelded wheel you can use to check the backspacing, offset, and clearances before ordering a new set of wheels. Once you've determined the perfect wheel measurements for your truck, you return the wheel, and your new wheels will be built to your exact specifications. We tried the new service on this Hardbody, and the results were fantastic. We avoided changing lug patterns on this truck and received a set of 18- and 20-inch wheels that bolted right up and cleared the fenders with almost no modifications. Sound good? Let's get started then.  1.& 2.Picking up where we...  1.& 2.Picking up where we left off, it's time to install a new set of front shocks. We chose Toxic shocks. The big-bore piston diameter and stiff-dampening characteristics are perfect for a mini-truck equipped with airbags.  2.  3.To make room for the new...  3.To make room for the new shocks, we must first trim away this section of the inner fenderwells and cut the brake line mount from the framerails.  4.After cleaning the grease,...  4.After cleaning the grease, dirt, and paint from the framerails, the shock mounts were clamped in place in preparation for welding.  5.A 110-volt MIG welder was...  5.A 110-volt MIG welder was then used to burn the 1/4-inch-thick mounts in place. The mounts were welded top to bottom to ensure that they will never break away from the framerails.  6.Attaching the lower shock...  6.Attaching the lower shock mount is easy because Nissan Hardbodies have a sleeve built into the lower control arms. Drilling through each side of the control arm with a 1/8-inch drill bit allows us to insert a 9-inch-long Grade 8 bolt and sleeve into the control arm and through the lower shock eye.  7.The universal four-link...  7.The universal four-link and airbag kit from Thorbecke Fabrication is filled with high-quality laser-cut bracketry, Firestone airbags, and beefy link bars. The lower bars are made from thick, square tubing with urethane bushing ends and are perfectly suited for mounting the 'bags to. The upper bars are made from round DOM tubing and feature threaded bushing ends to make adjusting the bars a snap.  8.Before IMZZ started the...  8.Before IMZZ started the process of 'bagging the rear end of the truck, it was hoisted into the air on a hydraulic chassis lift.  9.The rear of the frame is...  9.The rear of the frame is then stripped of the leaf springs, the fuel tank and mounts, and shocks. The exhaust piping was cut off just in front of the stock muffler.  10.The outer step notch plates...  10.The outer step notch plates were clamped into position on the framerails above the axles. Then the stock fuel tank mounting crossmember was plasma-cut away from the chassis.  11.After welding the inner...  11.After welding the inner and outer notch plates to the framerails, the top plates were cut precisely to length on a bandsaw and then test-fitted to the step notch.  12.Once the top plates were...  12.Once the top plates were MIG-welded in place, IMZZ is able to plasmacut away the stock portions of the framerails between the step notch. Note that both the fore and aft sections of the framerails are supported with jackstands to prevent the chassis from bending during its reconstruction.  13.Here is a good photo of...  13.Here is a good photo of what the frame should look like once it's been cut away beneath the step notch.  14.As with the rest of the...  14.As with the rest of the mounts from Thorbecke Fabrication, the inner gusset plates for the step notch are universal and must be trimmed to fit the width of the Nissan's framerails. This notch is large enough to accommodate a 22-inch wheel and tire package if not trimmed down.  15.Once the framerails have...  15.Once the framerails have been notched, James plasma-cut the stock leaf-spring mounts from the chassis since we'll no longer be needing them and they'll keep the truck from laying flat on the ground once it's been 'bagged.  16.The four-link mounts were...  16.The four-link mounts were positioned on the rear axle tubes so that the lower bars sit inboard of the framerails and the upper bars are triangulated inward toward a crossmember we've installed just behind the cab. The reason for this unorthodox method of bar triangulation is to give the 'bags plenty of room to travel on the inside of the framerails.  17.In this photo, you can...  17.In this photo, you can see the forward mounting crossmember for the upper link bars. The lower bars are parallel to the framerails and we are now test-fitting the 'bag mounts. The goal is to position the 'bags in the center of the bars to provide a high level of adjustability without making the truck ride too soft. We could have moved the 'bags forward toward the link bar's pivot point, but then the 'bags would only need about 10 psi to lift the truck and that would result in a sloppy ride.  18.Once were satisfied with...  18.Once were satisfied with the location of the 'bag mounts, the framerails were plated and the mounts were welded in place.  19.We chose a pair of Explorer...  19.We chose a pair of Explorer ProComp ES9000 shock absorbers to damp the rear suspension of our Nissan. These particular shocks have a collapsed length of 12 inches and an extended length of 25 inches.  20.The best way to mount shocks...  20.The best way to mount shocks is straight up and down, while still maintaining maximum travel of both the shock and suspension. In our application the best way to do this was by bending a custom upper shock crossmember in the M-Tech Supply Model-3 tube bender.  21.Our new crossmember was...  21.Our new crossmember was welded directly on top of the step notch and measured just 3 inches tall and 41-1/4-inches long.  22.The upper and lower mounting...  22.The upper and lower mounting tabs were welded in place at the same time. To ensure that the truck would lay out, we put the framerails on the ground, compressed the shocks until 1/2 inch of shaft was left before they bottomed out, and then tack-welded the mounts in place. The shocks were then removed and the mounts were fully welded.  23.With the suspension work...  23.With the suspension work completed, it was time to find a set of wheels that would fit our six-lug truck and tuck in cleanly. Boyd Coddington Wheels sent us this un-welded wheel to test-fit on the truck. This wheel helped us determine that to make a 20x8-inch pair of wheels tuck into the rear, we'd need 6 inches of backspacing and we'd have to trim the inside edge of the bed sides. Up front we'd need a pair of 18x8-inch wheels with 5.5 inches of backspacing to tuck inside of the 4WD front sheetmetal.  24.Sure enough, this beautiful...  24.Sure enough, this beautiful set of Boyd Coddington Magneto six-lug wheels and Toyo Proxes tires fit the bill perfectly. The tires measure 215/35ZR18 up front and 245/30ZR20 in the rear.  25.With the rolling stock...  25.With the rolling stock in place, we were able to cut out the bed to clear the frame and tires. Eventually, this truck will receive wheeltubs and a new sheetmetal bed floor to clean things up.  26.W.E.C. Air Systems provided...  26.W.E.C. Air Systems provided eight of these trick 1/2-inch ported valves to control each corner of our suspension system.  27.Each valve received a ground...  27.Each valve received a ground wire that was bolted to the mounting crossmember and a color-coded wire from the switch box.  28.This W.E.C. plexiglass...  28.This W.E.C. plexiglass switch box was filled with 10 Carling switches that will control each corner of the suspension as well as several moves such as pancake, seesaw, and side-to-side.  29.A 1/2-inch DOT-approved...  29.A 1/2-inch DOT-approved air line was routed from each valve to the brass fittings at the 'bags. It's important to use either a good pair of hose cutters or a sharp knife to cut the lines nice and straight. This will prevent air leaks at the fittings.  30.The completed suspension...  30.The completed suspension after it's been plumbed and wired.  31.The last few details that...  31.The last few details that need addressing before this truck is ready to cruise are the air delivery and storage system. After installing the bed back onto the truck, a Viar 450C air compressor and 5-gallon storage tank were bolted in place. A 0- to 200-psi adjustable pressure switch from Master Image Customs triggers the air compressor whenever the storage tank runs low on air.  32.When all was said and done,...  32.When all was said and done, this Nissan laid like nobody's business and rode like a champ. After a quick trip to the alignment rack, we were hittin' switches and draggin' like there was no tomorrow.
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BOYD CODDINGTON WHEELS
861-A East Lambert Rd., Dept. SC
La Habra, CA 90631
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Thorbecke Fabrication
P.O. Box 167
Francisco
IN
47649
Dept. MT
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California Mini Truck Dismantlers
4002 E. State St.
Montclair
CA
91763
www.calminitruck.com
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Toyo Tire USA Corp.
6261 Katella Ave., Ste. 2B
Cypress
CA
90630
Dept. MT
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IMZZ Industries
140 Arovista Way
Brea
CA
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Viair Corp.
26072 Merit Cir., Ste. 111
Laguna Hills
CA
92653
Dept. MT
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Master Image Customs
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WEC Air Systems
12150 Bloomfield Ave., Ste. G.
Santa Fe Springs
CA
90670
Dept. MT
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Maximized - May 2013
Excuse me while I wipe the dust off of my keyboard *cough, cough*. There is an old saying that goes...
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