Slate's "GMC Motor Home" Homepage
This page covers the 23 & 26 foot motor homes made by GMC from 1973 thru 1978. This is not a commercial page and at this time I'll attempt to avoid conflicts with all related GMC MH suppliers. Since nobody is paying for this I provide no warrenty and the user (you) accept all risk in using this information.
Great effort is made as to the appropriateness of remote links but I can not be responsable for other's homepages. Additions, corrections and deletions are welcome and will usually be applied the same day as I become aware of them. If HTML or other errors are found, please let me know. Support is intended back thru Netscape 2.0 and Windows 3.1
For quicker downloading most photos and greater details are provided with links indicated by standard html highlighting.
For those owners of other brands and those who do not 'know' the GMC here is a brief discription.
These GMC coaches were delivered in both 23 and 26 foot lengths from 1973 thru 1978. They were built on the GMC coach (bus) assembly lines and came in both the motorhome version which was finished by other motorhome companys and a Transmode version. The Transmodes often were used as airporters, radio stations and mobile banks among other things but most have since evolved to motorhome use. Because these coaches are front wheel drive, the chassis (frame) could be centered between the wheels rather than above the suspension componets and drive line. This allowed for a lower and more stable vehicle (at the expense of underfloor storage).
The engines and transmissions were derived from the current model year Oldsmobile Toronado and share both the drive line and a surprising number of suspension and steering componets. The earlier units having the 455 ci engine and the later units the 403 ci engine, both equipped with the Toronado 3-speed (Hydramatic 425) automatic transmissions.
Like the Toronado, the front suspension is twin A-Arms sprung with torsion bars running back under the front seats (near the ground). The rear suspension is what I call a 'bogey' type. Each side has two semi-independent rear wheels. The front bogey supported with a leading link and the rear bogey with a trailing link, very simalar to the trailing link on a motorcycle. Between the two is one air bag that acts as the spring. Air pressure is provided by a 12 volt powered one or two cylinder air compressor and is adjustable from the drivers position or automatically as road conditions demand. Since the air bag is mounted between the bogeys, not to the frame, road noise is greatly diminished as is the tendency for the vehicle to rock. This is no more apparent then in the sales lot when one steps into a GMC after being in some other SOB (some other brand). It's actually hard to make a GMC rock.
As the bogey assemblys mount to the outside of the frame rails no suspension componets cross the width of the coach except the front sway bar.
The frame rails are about 7 inches tall and the exhaust system is routed down the inside of the passenger side frame. The coach is mounted directly above the frame and the waste water tank and both 25 gallon fuel tanks are mounted between the frame rails. The fuel tanks are plumbed as one tank and only one filler is used although the plumbing scheme provides for about 5 gallons of reserve fuel to be available from either tank.
The body is constructed of a blend of aluminum and fiberglass. Typically the large flat panels are aluminum and the areas with compound curves are fiberglass. Other than the vehicle chassis (the frame) which is steel, all of the coach frame is aluminum. The firewall is aluminum as all areas requiring metal structural sheets. No structural wood is used anywhere except in the floor which is made rigid with 3/4" plywood, which is clad on the exterior in aluminum for weatherproofing. The roof is one piece of aluminum on aluminum structual members. These GMCs are very solid.
Only one door is provided on the GMC although in the movie Twister, that GMC has a driver's door! On the 23 foot unit the door is behind the passenger front seat while on the 26 foot unit it is somewhat further back. Unlike most other brands the floor sits very close to the ground. Although no step were provided by GMC, some owners have added one. Consider that next time you climb into a modern RV. Probably only the Vixen Motorhome has a lower floor.
The GMC has windows, lots of BIG windows. Ours has a couch behind the drivers seat, the back of which can be lifted and attached to the ceiling providing a suspended bed with a bed below it. Behind the passenger side front seat is a four seat dinette which also makes into a bed. Behind the dinette is the door. The 12 vdc compressor type refrigerator is next with the central vaccum system installed under the fridge. Next is the bathroom with shower, the electric water heater (assisted with a engine heat exchanger) being installed under the bathroom sink. At the rear of our GMC is the master bedroom with the propane tank and fresh water tank mounted on the rear of the right side of the vehicle. The rear bed makes into a dinette type area but most owners always keep it set up as a bed using the area under the bed for storage.
Behind the bunk bed on the drivers side is the kitchen counter, sink and gas stove with microwave oven with the gas furnace mounted under the counter. Then we have dresser type drawers with the air compressor system and a high current 12 vdc power supply/charger and the 130 vac, 40 amp circuit breaker panel in the bottom drawer area. On the rear left (drivers) side is mounted the ONAN 6 kw generator set and a very large storage battery (4D) that provides coach power when other power is not available.
All lights, fans, the water pump, furnace and refrigerator run on 12 volts DC, only. The only items that don't run on 12 volts DC are the microwave oven, the regular oven's electric warmer, the water heater and the roof mounted air conditioner. (In reality the refrigerator uses a 36 volts ac compressor but the power still comes from the 12 volts DC thru an invertor. The refrigerator does not have to be level to operate!)...return to index
Problems & Solutions
This may appear to be a lot of problems. Keep in mind the age of the vehicle and the total miles. Also note that we usually tow either a heavy boat, a car or a jeep, often thru the Rockys and on lots of dirt roads. Comparitively, I don't feel we see any more problems than I would with a modern coach that has seen the same service. Note that the repair parts prices are reasonable, very reasonable compared to that of modern vehicles.
- 10-1996, Need windshield wipers. NAPA refill # 60-2005, $12.73
- 10-1996, Need clearence light lens. Signal Stat # 1150A & 1150R, $2.00
- 10-1996, Started running lousy on trip. Extreme lack of power. Cleaned carbuerator in place with spray on type carb cleaner. Very effective. (This has been a continueing problem about every 2,000 miles. Suspect cylinder power imbalance due to worn cam causes excessive exhaust crossover in intake manifold resulting in carb overheating and boiling of fuel in carb after engine is shut off.)
- 10-1996, Lost coil in cruise control. Wrecking yard, Olds. Had to mix parts from old and older unit as drive cable connections were not the same. (Did not try to purchase from dealer.) $5.00
- 11-1996, Brake master cylinder. Checkers Auto Parts #??, $18.00 +/-
- 1-1997, Bad fuel line in area of left bogeys. Ran coach low on fuel. Raised coach high with air pressure and blocked up. Removed fuel tanks and replaced all soft fuel lines.
- 3-1997, 160,000 miles. Had transmission rebuilt although no problems were apparent. I removed & installed. $550.00 with torque convertor.
- 7-1997, Radiator tubes started leaking in Alabama due to fatique. Re-built radiator 6,000 miles later after finishing trip. Replaced waterpump and timing chain at same time due to convenience. New timing chain set cost me a lot of torque and 3-4 mpg. Suspect cam needs to be retarded. Prior to new chain, round trip to Des Moines (1300 miles) would average 13+ mpg at high speed, now 10-11 mpg. Now harder to pull boat out of lake also.
- 10-1997, Lost alternator in Corpus Christi, Texas. Rebuilt with kit from parts store with bearings, brushes, regulator and diode triode(?). $9.50
- 6-1998, Wife had rear tire blow out while criusing near Omaha, Nebraska at about 85 mph. Ripped air lines off of air bag. Good looking tire failed due to age. Wife made temporary repaire to air lines, changed tire and brought it home. New 16.5 XPS's tires all the way around. Should have gone to 16" tires/rims as 16.5's are not very common and carry a premium price, high enough to justify new (preferably alloy) wheels.
- 11-1998, 185,000 miles. Burned a valve towing 6,000 lbs boat over 10,000 foot Cameron pass. Rebuilt both heads on 403 engine. About $250.00. Also closed off intake manifold exhaust crossover and removed the valley pan at the same time which seems to have cured the carbuerator fouling problem.
- 12-1999, Lost right front bogey pin near Reno. Cause, corrosion. Moral, lubricate to remove moisture, especially after parking in the ocean! (While camping on the beach on San Padre Island, an especially high tide put the coach in the ocean. Although the coach was washed into the sand to the frame, the water did not rise above the frame. We spent about 4 hours washing out the coach from the floor down.)
- 12-1999, (Same trip). Burned out both mufflers between Donner Summit and Sacramento. Installed straight pipes in place of mufflers for trip home.
- 3-2000, Dissasembled to repair right bogeys. Ordered new pins and bearings but the new pins were of such poor quality I returned them. Installed new bearings and re-assembled with the old pins for temporary use. Increased tailpipe size to one 14 foot length of 3 inch tailpipe.
- 9-2000, Installed new custom made right side bogey pins. Installed new bearings and re-assembled. (New pins do not require removal of bogey housing. Design being tested).
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Dumb and Good Ideas
(contributions requested, especially for dumb ideas!)
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Just press "Back" on your browser to return from the photos.
GMC-1.JPG, Viewed from front right.
GMC-2.JPG, Viewed from front left.
GMC-3.JPG, Viewed from rear left.
starsr71.jpg, Nose to Nose with SR-71.
star_sr7.jpg, True Perspective of above.
(I've since been told this is an A11 or A12. It is at the battleship park in/near Mobile, Alabama and with-in the month I should have the visit it, get the tail number and know for sure.)
stardses.jpg, GMC at Telescope Site. Other Hobby.
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GMC Owner Homepages, Not For Profit
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GMC Owner Resources, Not For Profit, Clubs
Unless requested, not for profits will be listed without phone numbers. E-mail me for changes.
- GMC Cascaders, PO Box 361, Vashon, WA 98070, Club.
- GMC Classics, HCR 2, Box 6c, Medina, TX 77055, Club.
- GMC Colonial Travelers, 374 Overlook Road, Pleasent Valley, NY 12569, Club.
- GMC Dixielanders, Rt 8, Box 1230, Hickory, NC 28602, Club.
- GMC Elegant Criusers, 4735 Majorca Way, Oceanside, CA 92056, Club.
- GMC Forty Niners, ??90 Chestnut Street, Hanford, CA 93230, Club.
- GMC Gateway Motor Cruisers, 4897 Schumacher Road, High Road, MO 63049, Club.
- GMC Great Lakers, 261 Chambers Road, Mansfield, OH 44903, Club.
- GMC Heritage Cruisers, 36 Dicksen Street, Cambridge, ON Canada N1R 1T4, Club.
- GMC Motorhomes International, 571 Province Road, Barrington, NH 03825, Club, Technical Information.
- GMC Mountainaires, 980 Ridglea Way, Boulder, CO 80303, Club.
- GMC Nor'Easters, 11 Jerico Drive, Old Lyme, CT 06371, Club.
- GMC Pacific Cruisers, 5300 E. 28th Street, Long Beach, CA 90815, Club.
- GMC Saguaro Jetset, 6560 West Trails End, Tucson, AZ 85745, Club.
- GMC Six Wheelers, 1514 East Resthaven Road, Peoria, IL 61615, Club.
- GMC Sunshine Statesmen, 158 Old Tamiami Trail, Naples, FL 33942, Club.
- GMC Tidewater Crabs, 130 Doncaster Road, Joppa, MD 21085, Club.
- GMC Western States, 58 Tuscaloosa Avenue, Atherton, CA 94027 Club, GMC Preservation.
- GMC Yankee Clippers, 151 Moosup Pond Road, Danielson, CT 06239, Club.
- Greater Midwest Classics, 100 Brunswick Avenue North, Golden Valley, MN 55422, Club.
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GMC Owner Resources, Commercial
Unless requested, commercial resources will be listed with phone numbers, the numbers have not been verified. E-mail me for changes.
- Alex Sirum Auto, 2013 S Parrott Avenue, Okeechobee, FL 34974, 941-763-1121, Sales, Service & Parts
- Blak, Inc., P.O. Box 25, Sumner, IL, 62466, 618-936-2922, Cross Reference Catalog
- Bethune Sales Company Inc., Davidson, NC, 704-896-7137, 1996 GMC II, Remanufactured GMC's
- Buskirk Enterprises Inc., 195 S. Stoutenburg Road, Sandusky, MI 48471, 810-648-3963, Parts & Service
- Cinnabar Engineering, Inc., 116 Orval Street, Sandusky, MI 48471, 800-720-2227, OEM Parts Supplier
- Gateway Motorhome Company, 1-800-654-0374, Parts
- Gear Masters Inc., 6786 Piccadilly, Houston, TX 77061, 713-649-4708, Fianl Drives
- GMC Motorhome Marketplace, 7091 Broadway, Suite D, Merrillville, IN 46410, 219-769-7733, Magazine
- Golby Motor Corporation, 7600 S Orange Avenue, Orlando, FL 32809, 407-859-9000, Sales, Parts & Service.
- Grandview Motorhome Classic Restoration, 13880 Weaver Road, Marysville, OH 43040, Restoration & Service
- Northern California Classic GMC Service, 415-456-1904, 541 Irwin Street, San Rafael, CA 94901, Service
- Osburns R.V. Service, 6001 Holly NE, Albuquerqe, NM 87113, 505-821-0543, Sales, Parts & Service
- Ragusa Pattern Shop, 1920-D E Warner Avenue, Santa Ana, CA 92705, 714-261-5898, Custom Castings
- Southland Enterprises, 3000 Buford Hwy., Buford, GA 30518, 770-271-7502, Parts & Service
- Winterfeldt, 5468 Gunbarrel Road, Longmont, CO 80503, 303-530-4995, Engine & Drivelines
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Units & Items For Sale or Wanted
While providing links is under my control the information in these links often is not. If you find any listing that is improper, in error or would like to list or un-list something, let me know via 'firstname.lastname@example.org'.
No items listed
I suggest that you look in the Owner Homepage area also.
Wanted: Just Dreaming
The means to vary the valve timing, duration and profile while driving. I feel that both improved emissions and increased fuel mileage is not only desired, it's mandatory. Our smog is not always going to be acceptable yet I feel these high nickel Old's engines can not be beat for durability. Prefer full electric valve solenoids such as Aura Systems and others are developing. (Lately little information is available on Aura System's electromagnetic valve actuators but I have faith that somebody will make them feasible.)
Direct drive engine driven constant frequency alternator so we can get rid of the weight of the Onan and move all of the air-conditioning from the roof and engine compartment to the generator compartment. This would also allow the removal of the condensor from in front of the radiator which would then allow an electric radiator fan. (Due to the thickness of the radiator and condensor, electric radiator fans do not provide enough air flow and can not be used very successfully.) Lots of power and engine cooling benifits including the ability to reverse the fan when the vehicle is stopped to greatly reduce engine compartment heat. In practice, this is done with a large 140 VDC alternator whose output is then converted back to 115 VAC. (230vac 3 phase might be even better due to more reliable motors and readily available invertors.) The DC to AC part is easy and cheap as long as you start with at least 140 VDC. 4kw at 700 engine rpm is somewhat more difficult. Once again, Aura System has the product but it is beyond my price range. Their distribution (sales) system sucks also as it does not allow owner installation, probably because of potential throttle connection liabilities. I do not feel that 4kw, 12vdc to 120vac invertors are practical as the high currents required provide to many dangers and the electronic componets are to expensive compared to the higher voltage devices.
Electric shocks that double as linear actuators/springs so they can be intelligently controlled. This could provide active roll control in place of sway bars. One advantage over conventional sway bars, besides flexability would be reduced body stress in extremely un-even road conditions. These shocks have to be able to provide motion as well as arrest it.
Full (diesel/)electric motive drive to all six wheels. Spinning the tires sucks as does not having the engine at the best torque/effiency rpm. Regenning' the energy back into the engine cooling system would then allow us to run down the hills without fear of a run-away. Safer slick road braking should also result almost to the possible elimination of the hydraulic brakes. Requires practical 30kw motors and a small, lightweight 150 to 200 kw generator. The basic switch gear is simple if not real cheap, yet. Note also that 200kw diesel engines weigh to much.
115 vac electric servo assisted steering and engine coolant water pump. No fan belts!
Note: 12 vdc is great for the battery and for rough service lamp filaments but otherwise sucks. 12vdc requires heavy wires (in pounds) and high currents which can lead to greater fire danger. 115vac, single or poly-phase is less expensive, safer from a fire standpoint, lighter and motors runs longer due to lack of brushes.
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Our GMC & Some Trips
As of September of '96 we are the new and very proud owner's of a 1977 26' GMC. Although the pink slip calls our GMC a 1978 the plate at the door says 1977. We therfore call it a 1977 GMC. David with the registry tells us that it is a Kingsley model, which I agree with.
When we bought our GMC it indicated 51,000 miles. The owner made statements that make me think it really had 151,000 miles. The condition of the coach makes it hard to believe it has travelled that far but that is a statement as to the quality of the GMC's. The owner also said it had visited all 48 of the lower states, some of Canada and quite a bit of Mexico. As of today she has about 191,000 miles. She's a little more tarnished but still quite proud, as are we of her.
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Vixen Motorhome Stuff
A Vixen is a unique motorhome like the GMC. If I wanted a smaller highway burner that got 21-33 mpg for just one person, maybe two, this is what I'd look for... $18,000 to $32,000 range, 1986-89.
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Credits & Host Contact
created and maintained in DOS with a text editor
created 31 Dec 96
last edited 18 May 2006, Added Projects Link
barely maintained by email@example.com