GMC Motorhome owners have a multitude of resources to help them keep their coach on the road as well as offering engineering improvements.
Our GMC 49ers Club is fortunate to have many members who are highly regarded for their GMC Motorhome products, services and knowledge. Here's info on them:
Fay Curtis: Curtis Unlimited of Kneeland, CA - GMC Motorhomes have benefited with their Fiberglass and Metal Fabrication talents. http://www.bdub.net/curtis-unlimited/index.html Phone: 707-443-8523 Email:email@example.com
Eugene Fisher: Gene is a well-known GMC engineering resourse and has an extensive collection of GMC Motorhome information and links on his GMC Information website: http://gmcmotorhome.info/ Email: firstname.lastname@example.org
Jim Kanomata: Founder of Applied GMC in Fremont, CA, is a full service facility equipped with a welding area, vehicle lift, parts supply and improve and repair GMC. http://appliedgmc.com/ Phone: 1-800-752-7502
Terry Taylor – GMC Motorhome Logos, Nick-Naks, License Plate holders and other “I wish I had that” for GMC owners. http://www.dldesignstore.com/
Manny Trovao – Manny’s Transmissions (including Switch Pitch) are built specifically for our motorhomes. 3.50:1 Power Drive chain and sprockets. Phone: 408-937-1583 Email: email@example.com
Jim Hupy – Master cylinder power bleeder, wheel hub extenders and GMC Motorhome service, 1754 82nd Ave SE
Salem, OR 97317. firstname.lastname@example.org http://bdub.net/jhupy/
More Technical Suppliers and Resources for the GMC Motorhomes:
GMC Parts & Services Suppliers - GMC Supplier Links
GMC Custom Products - GMC Motohome Products
GMCnet exists for the purpose of exchanging information and promoting discussion about the motorhomes manufactured by General Motors Corporation (GMC) from 1973 to 1978. It is a "closed posting" service meaning you must be subscribed in order to post questions, comments, and propose solutions.
GMC 49ers Blogspot -- gmc49ers.blogspot.com/
Air Bag Temporary Fix
Sometimes airbags fail and a replacement is not available (payday too far away). My 1975 Glenbook air suspension had leaks and was worrisome on long trips. If an airbag fails, a 13" long 4x4 post with a hole through it and a 3/4" threaded rod can be used to raise up the coach. This is OK for short trips but for long trips it's a rough ride.
My coach was in no shape for long trips with multiple issues. I wanted an inexpensive solution for the airbags, while I got the brakes and front wheel bearings in order. I reasoned that coil springs have been used on millions of Ford truck suspensions and found a way to mount them on the rear of a GMC Motorhome.
While my coach was stored in Colorado, I went shopping for an E350 van in a Longmont Colorado junkyard. They agreed to sell me the set of springs with perches and mounting hardware for $100. I worked on the coach in between business trips, carrying tools and parts with my luggage. At home in San Jose, I modified the E350 top spring perches by welding a 1/4" steel plate with a 3/4" hole in the middle to adapt them to the GMC wheel bogie. Amazingly, the bottom spring perch from the Ford will bolt directly onto the GMC bogie arm with a 3/4" bolt from the hardware store. The springs are out of a 3/4 ton van, they are strong, 600 lbs per inch spring rate.
The springs can be found in a MOOG catalog. They are 18 1/2" free length and 13" loaded with the GMC. The spring rate makes for a slightly stiffer ride than the stock airbags, but not rough. The ride is smoother than many cars I've ridden in.
I angled the top spring perch 3 degrees to make the spring sit flat when loaded. The spring perch will change angle more than it does in the Ford application. These springs were designed to work in Ford's Twin I-Beam suspensionm which has a lot of angular change. They have a smaller diameter at the ends to accommodate the angular change.
The hole in the perch is for a retaining clamp to keep the spring from falling out when unloaded. It would not fit on the GMC because it is too close to the tire. There is no problem with the spring coming loose on the GMC because the shocks limit the downward suspension travel. The outside diameter of the spring is less than 6 inches.
I've traveled over 5000 miles with this setup and experienced no problems It handles the roughest roads. And the higher spring rate reduces body roll significantly. The only disadvantage is having no height adjustment. I have to use ramps to level the motorhome when camping.
It's been 6 years since I experimented with coil springs. I now have a set of Harrison quad brackets with AirLift D2600 airbags. They ride very soft and can move up/down +/-4".
12/4/2016 B Wevers
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