THIS IS INTENDED FOR COBALTS WITH EIBACH SPORTLINE SPRINGS ONLY
Other springs may not have similar coil spring dimensions however if you obtain a set of bags that fit the installation is exactly the same. Air lift load assist springs Part number 60748 kit which fits a 1997-2004 Olds Silhouette APV are an exact fit for the sportlines.
Well here it is my first write up. Originally this experiment started on the .net site but I figured everyone could benefit from it. I unfortunately do not own a digital camera so it will be lacking real color photos of the subject matter however being a mechanic with access to GM Dealer World I borrowed, modified, and created some diagrams for the important stuff to try and make them as clear as I could. I originally came up with this idea after installing BMR drag bags in customers GTO. It’s supposed to prevent wheel hop in GTO’s at launch but it also significantly stiffens the rear end. After installing the FE5 front sway bar I noticed the car was displaying understeer. I had done everything already and needed a way of stiffening the rear suspension to create oversteer. I could have installed Progressives new 25 mm solid rear sway bar however I decided to give the bags a try. After some e-mails to Airlift tech assistance, they where able to supply me with a part number for a kit with bags that matched the dimensions I needed (above). So far the bags have done the trick and are adjustable too.
Step 1. Elevate the vehicle, remove the rear wheels and support the rear trailing arm.
Step 2. With vehicle weight on the rear trailing arm remove the top 18 mm shock bolts from both sides of the vehicle. Also locate and remove the two 10 mm nuts (one per side) holding the brake line brackets to the car. Remove the brackets from there mounts, this will allow the brake lines to hang with less stress on them.
Step 3. Elevate the vehicle to unload the rear springs and remove them from the vehicle along with the upper and lower spring insulators. The upper insulator may just fall out. The lower will require proper motivation to be removed from the spring pocket, for example a large flat blade screwdriver and some anger.
Step 4. The upper insulator is a 2 part insulator. One is a hard plastic disk with the upper bump stop integrated into it. The other is a soft neoprene like disk that fits between the top of the spring and the hard plastic insulator. Measure from the flat portion of the hard plastic insulator down the bump stop about 1 inch, mark it and cut it. Feel free to remove a little less material from the hard plastic but when you are done the edge of the plastic should be about even with the upper metal bump stop that is a part of the car.
Step 5. The lower bump stop is the most labor intensive portion of the installation specifically because you need to trim the steel bump stop on the trailing arm. Measure the lower insulator just like the upper and cut it. Reinstall the insulator back on the trailing arm, and mark the trailing arm accordingly. Remove the insulator and cut along your mark. I used a high speed fiberglass cutting disk on an air powered “wizzer”. Be careful sparks and debris will fly, wear safety glasses and don’t cut too much. After you have removed the bump stop top, grind the sharp edges. You should have to chamfer the outer edge in order to reinstall the lower insulator and don’t neglect the inner edge either. To fully seat the insulator a hammer may be required. Make sure the edges are relatively smooth to avoid cutting or puncturing the bags. The insulator and bump stop should be dead even with each other.
Step 6. Install the bags in the rear springs, it’s not hard to do but it’s not easy either. Remove the black cap from the fitting on the bottom of the bag. Squish the bag down and reinstall the cap. Stuff the bag into the spring and then remove the cap again.
Step 7. Now’s time to start running the air lines. Insert the line down through the trailing arm and out the back opening. I have a progressive rear sway bar and I used that to zip tie the airline too for routing up the trailing arm. I routed the driver’s side line up and across the sway bar to the passenger side of the vehicle to keep it away from exhaust heat. Then up over the rear brake line, across the top of the fuel filer neck just under the frame rail to the rear black plastic fascia. I chose to keep the bags separate, driver and passenger, so I could add extra pressure to the driver’s side airbag. The supplied line was just long enough for me to do this so keep it loose but not so loose it flops around. Reinstall the upper and lower insulators and springs. Slide the air line up onto the bag and secure it with one of the supplied clips. Shove the bag to the bottom of the spring making sure you have some slack in the supply line because when you raise the vehicle later the inflated bags will slide up with the springs as they uncompress.
Step 8. Load the rear trailing arm and reinstall the 18 mm shock bolts and the brake line brackets with there 10 mm nuts.
Step 9. Install the supplied valves where you can at the rear of the vehicle. I installed them on the rear black plastic fascia and because of placement I had to remove some metal from the body to prevent rubbing on the line. Inflate the bags carefully. They are small and inflate quickly if you are using any kind of compressed air. I set mine to dr.side 16 psi and the pass. side to 15 psi. Max recommended pressure from airlift is 25 psi.
Step 10. Reinstall the rear wheels and torque to 100 lbs. ft., lower the vehicle, drive and enjoy.
Step 11. (optional) With vehicle weight on the suspension inspect the driver’s side bag/spring and its proximity to the exhaust. I recommend fabricating a heat shield to protect the bag itself from any potential heat radiated by the exhaust.