Installing Airlift 1000 Load Assist kits on the MN12 platform
Written by: Rod Maksimovich (Racecougar)
If you are looking to add a little adjustability to your rear ride height and firmness, prevent the rear tires from contacting the quarter panels, or add a little extra load carrying capacity, the Airlift 1000 Load Assist air bags are the “go to” solution. These inflatable bags are installed inside the rear coil springs and can be inflated/deflated at the supplied Schrader valves via an external source (shop air compressor) or they can be installed along with a Airlift on-board Load Controller compressor kit.
Two kits are offered for the MN12 platform. Kit number 60789 is designed for the 1989-1991 MN12, while kit number 60776 is designed for the 1992-1997’s. The difference between the two kits is due to the factory bumpstops inside the rear coil springs on the 1989-1991’s.
Regardless of the model year of the MN12 you intend to install the air bags onto, I’d recommend purchasing the kit intended for the 1992-1997’s (p/n 60776). The greater volume of the later model bags makes it much easier to dial in the air pressure present in the bags. Installing the later model bags into a 1989-1991 chassis also allows for the lines to be hidden away inside the framerails, as opposed to dangling below the lower control arms.
The air bag on the left is from the 60789 kit, while the bag on the right is from the 60776 kit. Notice the difference in volume between the two.
So let’s move on to the installation process…
To get started, you’ll need to safely remove the rear coil springs and swing the lower control arms down and out of the way. I won’t go into a step by step here, as any good repair manual should cover these steps.
For those working on a 1989-1991 chassis:
With the coil spring and lower control arm out of the way, the factory bumpstop can now be removed. Using either a large crescent wrench (or 2-1/2” combination wrench if you happen to have one) to grab the flats or a pipe wrench to grab the body above the flats, simply unscrew the factory bumpstop from the framerail.
1992-1997 guys can join back in here:
Now, since we’re going to install the air bags inverted from the orientation described in Airlift’s instructions (nipple pointed upward, lines hidden in the framerail), we need to create a space for the nipple and line to pass through the upper spring perch.
Use a 1” holesaw, centered on the small hole already present in the upper spring perch, to create a clean hole for the nipple/line to pass through. Be sure to file and smooth any burrs or sharp edges to prevent damage to the airbag and line. Seal any bare steel with paint to prevent rust.
Now we can route our line. I prefer to locate the Schrader valves in the spare tire wheel in the trunk, as I’ve found it to be an easily accessible location. Using a long piece of fish tape, bailing wire, or the like, route the air line through the framerail from the new hole in the spring perch to the rearmost factory hole in the framerail.
Before attaching the line to the airbag, slip the airbag inside the coil spring, place one of the supplied spring clamps on the line, and apply a dab of RTV or similar sealant on the nipple of the airbag.
Gently pull the excess line through the framerail as you place the coil spring back into place on the upper spring perch. Raise the lower control arm, seat the bottom of the spring on the lower spring perch, and reassemble the suspension.
As mentioned above, I prefer to install the Schrader valves in the spare tire wheel inside the trunk for ease of access. I advise against teeing the lines together to one Schrader valve, as that will exacerbate vehicle lean when cornering and will also eliminate the adjustability afforded by keeping the airbags isolated from one another. For instance, when drag racing, it is common practice to increase the air pressure in the passenger side bag in relation to the driver side bag.
Using a 5/16” drill bit, drill a hole for each valve and install them using the hardware supplied in the kit. Cut the air line to length, place one of the supplied spring clamps on the line, apply a dab of RTV to the nipple of the Schrader valve, and install the line.
Before reinstalling the wheels/tires and loading the suspension, place 5-10 psi in each airbag and locate the bag up against the upper spring perch by hand, with the nipple/line centered in the hole drilled earlier. Replace the wheels/tires, set the vehicle on the ground, inflate the bags to your preferred pressure (between 5psi and 25psi), and enjoy!