Seattle Collision Center
1752 Rainier Ave South
Seattle, Wa 98144
SULLYBILT REPLACEMENT AIR SPRING
The air spring suspension system on the GMC motor home produced from 1973-1978 has functioned well in its original design for decades. Many coaches are still supported by the original Firestone air springs. The original air spring design performs all of the leveling and weight support for the coach while driving down the road or adjusting the coach to a level condition while parked for camping. New replacement air springs were available through various distribution channels until recently when Firestone halted production of the original part # and have failed to offer a direct replacement to take its place. There have been many unique designs offered to replace the original GMC air spring system. These different systems vary in complexity, price, ease of installation, as well as similarity to the original system function. The Sullybilt air bag mounting system is the least expensive replacement option available that retains factory like ride height adjustability. It is also the simplest and easiest to install.
The Sullybilt air bag mounting system is a refinement of a concept published by Mark Grueninger of Valmeyer Illinois. In the course of his business Mark had access to a number of different air springs and started doing research and tinkering. The original Markbag was the result. In building my own set I made a few discoveries of my own which led to several changes in design and construction techniques implemented for manufacturing. The Sullybilt air spring system is the result. The main changes made prior to production were;
Installation of the second spring kit will go faster than the first.
Watch the Installation Video.
Sullybilt air spring bracket kits are available individually or as a complete set. A complete set will do both air springs. Individual spring kits can be installed on only one spring but I recommend replacing both air springs for an even, consistent ride and keeping one functional OEM spring on board the coach as an emergency spare. Individual bracket kits come with all needed hardware to install with the exception of one of the original air spring nuts and washers which are retained from the removed OEM spring.
Bare steel brackets $190 per side or $375 for a complete set.
Hot dip galvanized steel brackets $220 per side or $400 for a complete set.
Stainless kits firm pricing to be quoted at time of order due to the fluctuation in stainless pricing.
Shipping is $17 per side or $34 per complete set.
Powder coated brackets. With the massive variety of powder colors/textures and manufacturers I am reluctant to offer a multiple of color choices. I can have them powder coated black if a complete set is ordered and the cost will be $125. If you want powder coat and want to pick a custom finish I recommend purchasing the bare steel brackets and taking them to a powder coater of your choice near you so you can pick the color at the facility. I think that you will find that you can have a complete set done in the color of your choice for less than I have quoted here for black.
Above pricing does not include the air spring itself. The air spring is a Firestone manufactured air spring part # W01-358-9294. There are other cross referenced springs available. A cross reference sheet as well as a spec sheet on the Firestone air spring is available on the Firestone corporate web site and included with each side set of Sullybilt air spring brackets.
Available on the web from ~$118 each, here is a web search for the required air bags:
I have had the Sullybilt system for about a year and have only driven about 2000 miles since installation. I purchased it with a lot of apprehension. I was torn between the Quad bag and Sullybilt. I spoke with Todd on the phone a couple of times and with some reassurance I finally decided to go with his system based on the price difference. Seldom does going with the lower priced item turn out well for the purchaser. I am happy to report that this product does not follow that rule. I have been incredibly happy with this system. It runs at much lower pressures, rides and handles great and it takes some of the harshness out of hitting potholes(which we have a lot of in South Dakota). This is not a comparison or an insult to any other aftermarket system it is just my experience, for what its worth.
I was able to find a volunteer to try the new bag bracket set up at the GMC rally in Ferndale a couple of weeks ago. The weather was cold and drizzling not to mention getting dark by the time we gathered a small group to watch the install. We decided to install one bag for a side to side ride comparison. After a few minutes on soft uneven ground the new bag was on and the system aired back up. Minutes later we were out tearing up the neighborhood and turning corners both directions at speed. There was the coach owner and driver at the wheel, myself and two other curious GMC owners in the coach. The observations were
1. The ride appeared to all of us to be firm but plush and very similar to the OE.
2. There appeared to be less body roll or lean when turning away from (loading) the new bag design than the oem. The new bag system was installed on the right. Left turns which load the right bag resulted in less body roll or sway than right turns which load the left oem bag set up.
3. There should be less sway or lean with both bags installed than currently exhibited by the stock system
4. No additional parts were required as the existing air lines and brass adapter swapped over without incident. No jacking was necessary to instal the bag even on soft uneven out of level ground.
5. The owner and driver of the test coach said he loved the feel and thought it felt better than the oem set up.
6. The owner and driver of the coach is the first order placed and will have his stainless set next week.
Aug 15, 2012
Wanted to take a moment to praise Todd Sullivan and the Sullybuilt airspring brackets. Ordered the first set which sat too close to the wheelwell. Spoke to Todd and long story short, he developed a second "offset design" which fits perfectly. I guess all GMC rear wheelwells are not equally placed, likely common on a mostly hand built vehicle.
Sent the new ones out and I sent the first set back. Installation is so easy, takes longer too jack it up and take off the wheels.
Got them on a few weeks ago and took a long test drive. Wow! What a difference. I was puzzled why after a complete rebuild of my front steering and suspension, it still did not drive right. Well it does now. Never thought upgrades to the back would help the front so much. Drives with one finger now. Less roll on a turn.
Am 100% satisfied. Even sold off my used OEM bags to buy an extra firestone airspring to keep for a spare.
Excellent product with excellent service. Thanks again
Mark Grueninger's original design