1971 Chevrolet Suburban KPC Airbag Suspension Install - Next Day Air

KP Components and AVS Make for a Sweet Ride

Maxwell Matthewson
Jun 1, 2013
Photographers: Maxwell Matthewson
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Despite the tough economy there are still badass trucks being built and reputable companies around to get you the custom parts that you need. We are currently working with a local shop, Unrestricted Auto Trends in Lake Elsinore, California, building a 1971 Suburban. The owner of the truck wanted a complete bolt-on system that would lay out the 'Burb while maintaining a great ride. KP Components, a division of Chris Alston's Chassisworks, makes an entirely new suspension for the '67-'06 GM trucks and SUVs. Their cantilevered four-link kit (PN: KPC 4CBO-C31, $1,753) is by far one of the nicest riding bolt-on airbag suspensions around. To complement this, we also ordered their front LayArm kit (PN: KPC LAB-C41, $2,008). Together, these kits will bring the Suburban down while keeping it riding smooth. The suspension parts are just step one, as we'll also need all of the air components to complete the install. We contacted AVS for the air line, airbags, valves, tanks, switches, and even wiring. AVS has great prices and fast shipping so you can get to work trasnforming your ride. Follow along as we turn this Suburban frame into a low roller in two days.
This is a fairly complex setup, but it didn't require any off-the-wall tools. Basic handtools would suffice, making it possible to install it in your driveway.
1. Here is the 'Burban's frame before the install. We had it stripped and a quick coat of black paint was sprayed on it. By the end of this article, the frame will be lying on the ground and able to tuck 24-inch wheels.
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2. We started in the rear. The first step was to drop the axle and remove the factory suspension. The track bar was pulled free of its mount and discarded.
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3. With the shocks out, we removed the shock mounts. This was accomplished by cutting an X into the rivets with a cut-off wheel. The rivets were then chiseled off and the mount pried from the frame.
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4. Finally, we used an angle grinder with a cut-off wheel to cut the coil springs in order to lower the axle from the truck. To keep the location of the axle in check, we left the link bars attached for the next few steps.
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5. Next, we removed one of the rear factory crossmembers using an air chisel. This was also added to the scrap pile.
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6. To start installing the KP kit, the included notch was set on top of the frame and the holes were marked. The area under the notch was also marked off so it could be cut.
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7. Again using an angle grinder, Jake carefully cut the notch out.
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8. After cutting the frame, the step notch was bolted in place. One of the cool things about this KP kit was that it included all of the necessary Grade 8 hardware. This ensures that it will hold up to everyday use without problems.
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9. With that complete, the next step was to install the new driveshaft carrier bearing crossmember, which is included in the kit. The factory unit was unbolted and set aside.
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10. The new crossmember slipped in between the framerails and used the factory holes for a seamless install.
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11. To remove the axle from the link bars, the U-bolts were cut and the axle was centered under the notch in the frame.
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12. Moving to installing the cantilevered four-link, the first step was to attach the link bar brackets to the frame. You can also see in this picture where the body mount needed to be trimmed to give the bracket more room.
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13. On the axle, the pad for the factory link bars also needed to be trimmed. This is where the new links will be mounted.
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14. After supporting the axle with jackstands, the link bar mount was bolted to the axle with new U-bolts.
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15. The next step was to assemble the link bars. All four bars have adjustable ends so the alignment of the axle can be fine-tuned.
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16. Again, using the included Grade 8 hardware, the link bars were bolted to the mount on the frame.
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17. The kit utilizes a cantilever behind the axle to offer a superior ride. This is the cantilever bracket. It was bolted to the frame mostly using the factory holes.
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18. The assembled cantilever lets you see how the system works, with the airbag sitting between the bars. Being behind the axle means that it is supporting more of the weight. The dog-bone link, which attaches the cantilever to the axle, comes in different lengths, depending on the wheel size you want to run.
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19. Since this kit is a parallel four-link, there is an optional Watt’s link (PN: KPC WLB-C31, $369) offered by KP Components to locate the axle between the framerails. To attach it to the axle, the diff cover bolts are removed and new, longer bolts are used to bolt the Watt’s link down.
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20. Another trick feature with the KP kit is the fact that it can be expanded upon without modification. Here you can see how the side mounts for the Watt’s link bars integrate seamlessly into the step notch.
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21. Before tightening all of the bolts down, we checked and double-checked to make sure the axle was centered.
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22. With everything finalized and bolted down, the Watt’s link was finished. It was then time to move to the front.
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23. Compared to the rear, the front is much less complicated. The first step was to remove the tie-rod ends from the spindle.
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24. Next, the sway bar was unbolted and tossed in the scrap heap.
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25. Finally, the coil spring was compressed, the upper and lower control arms were unbolted, and the whole assembly was removed and set aside in one piece.
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26. The new upper arm was bolted to the factory studs using new hardware.
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27. New drop spindles were bolted to the upper control arms with a castle nut and cotter pin.
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28. In order for the airbags to be mounted up front, a plate had to be bolted to the bottom of the coil spring bucket. You can see the holes for the bolts and the air fitting in the plate.
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29. To finish off the install of the LayArm kit, the lower control arm was bolted to the frame and the spindle.
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30. We gave AVS a call and ordered all of the air suspension components. They are a one-stop shop and had everything we needed to get the job done. Everything from the tanks and valves, to the switches and wiring kits, and even the Slam Specialties airbags (not shown in photo) arrived in only two days.
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31. After mulling it over, we decided to mount all of the air components behind the rear axle. We will then build a door in the floor of the cargo compartment of the Suburban to access all of the pieces.
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32. After mounting the tanks to the plate, we installed the air fittings. This one is in the top of the tank and will be used to connect the two tanks together.
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33. We will be running dual Viair 480C compressors, with one compressor feeding each tank. This should give us a fast refill time. Each compressor will be wired to its own relay.
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34. In the back of one of the tanks we installed the pressure switch that will tell the compressors when to turn on and when to turn off. This unit is a 160 psi on and 200 psi off. On the back of the other tank, we will install a relief valve, in case something goes wrong and the compressors don’t shut off.
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35. Finally, we could install the Slam RE-7 airbags and finish up the suspension.
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36. This had to be the last step because we needed to first install the airbags. These Varishocks are included in the kit and are made from billet aluminum and are double-adjustable. They have two knobs to adjust compression and rebound.
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37. After ensuring all of the bolts were tight, we ran the air line and tested the system.
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Fresno, CA 93703
Unrestricted Auto Trends
Lake Elsinore, CA 92530
KP Components.



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