This article originally appeared in the May 2021 issue.
Our big ride just got built up even bigger! That’s right: the suspension on our F350 Soup build just got even cooler and more sophisticated with the installation of new Air Lift LoadLifter 7500XL air bags with a WirelessAir 7400EZ controller. At Diesel Tech we plan on hauling some really heavy trailers, so we teamed up with PowerTech Diesel to get those heavy-duty air bags set up. The 7500XL air bags are Air Lift’s strongest air bags, offering up to 7,500 pounds of load-leveling capacity to level massive loads like they’re nothing. The large double-bellows springs provide greater leveling strength at lower pressures, and they’re easy to control with the WirelessAir controller. The installation of the entire system was completed by PowerTech technician Jordan Johnson.
Step 1: Preparation
Jordan began the work by taking all the air bag components out of the box and laying them out on a table. The rear bump stops also needed to be removed for this project, as the air bags would take their place. With those, the studs and gaskets also needed to be taken out and replaced with the new thread holds.
Step 2: Install Upper Frame Brackets
Next, Jordan installed the upper frame brackets for the bags on both the driver and passenger sides; he secured them by tightening the Allen bolts.
Step 3: Assemble Air Bags
It was now time to get the air bag components lined up and ready to mount. Jordan started that by screwing the air inlets onto the air bags’ round top mounting plates; then he put the plates on the bags. On top of those, he bolted on the hexagonal plates with the center bolts going in hex side up and the outer bolts going in hex side down. With the lower round plates subsequently attached to the bags, the bags inserted into the lower mounting brackets with the long studs below them and components bolted together. It was almost time to put the bags in their place.
Step 4: Install Air Bags
Jordan then began getting the insides of the fenders ready for the new air bags by removing the sensor wire and brake line mounts to make room for the brackets. Upon removing the fifth wheel mounting bolts and inserting the passenger side air bag’s inner mount, the air bag was then installed; he replaced the old fifth wheel mounting bolts with the new ones while doing that. The same process was repeated for the driver side. The brake line and sensor wire mounts were then reconnected and reinstalled where appropriate.
Step 5: Install Air Bag U-Bolts
The air bags are held in place by U-bolts, which Jordan then began to work on. He installed a silver U-bolt for the passenger side lower air bag bracket by placing it on the foot of the suspension leaf springs, which the bracket was adjacent to. He repeated the process for the driver side.
Step 6: Align & Finish, For Now
To align the air bags into the upper brackets, Jordan lowered the lift and tightened the nuts to close them together. He then raised the lift back up and tightened the fifth wheel bolts in the fenders. With the air bags now (mostly) installed, Jordan repositioned the brake line bracket on the driver side and retightened its nut; following that, he tightened up all loose nuts elsewhere.
Step 7: Mount Air Bag Compressor
It was now time to begin installing the air bag compressor, and a mounting location needed to be scouted out. It took a while, but Jordan found a spot on the underside of the truck’s body above the differential where he was able to insert a U-bolt with the threads pointing downward. He placed the compressor there and tightened the nuts, making sure the compressor cleared the other surrounding components. He had to use a deep socket to get to the nuts, as there was no room to use a wrench.
Step 8: Connect Air Lines & Filter
Jordan grabbed the supplied air line spool and cut the length he saw fit to go from the compressor connections to the air bag inlets for both sides of the truck. There was some slack, so he screwed clamps into the frame where needed. To mount the air compressor’s filter, he took off its plastic clip set and mounted it on the frame behind the compressor (toward the truck’s rear end).
Step 9: Finish Installing Air Bags
While he was at it, Jordan decided to finish up the mechanical work at the truck’s rear end. He lowered the truck to the ground. The large U-bolts that secure the air bag brackets by wrapping around the axles were not long enough to clear the axles with the small black bars, so he needed to cut same-size threads off other U-bolts and insert them into extensions on the axle threads. With that done, the black bars were inserted and fastened on the studs below the axles.
Step 10: Set Up Wiring
The compressor needed electricity to run, so Jordan started setting up the wires. After lifting the truck up for this job, he inserted the wires into the black looming and then routed them down the passenger side of the frame. He plugged the main control harness into the compressor and spliced the compressor’s ground and power inlets together with the outgoing battery wires. Finishing that part of the wiring up, he zip-tied it to mounts on the frame where appropriate.
Step 11: Connect To Battery
Jordan moved the battery end of the long ground and power wires up into an opening near the passenger side fender and under the hood. He attached a fuse connection onto the live wire just before its end and then connected the ends to the terminals. From the fuse connection, he ran the long pink control wire (already run alongside the power and ground) to a connection on the fuse box.
Step 12: Test System
All the wires were connected and secured, so the system was now ready to be tested. Jordan synchronized the remote controller to the system and then set the airbags to 50 psi. After they inflated to that pressure, he deflated them and re-inflated them to check for leaks. The air bags held up perfectly. The air bag and air system install was now complete.