Author Topic: GMC Motorhome  (Read 1104 times)

Offline AE_Collector

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GMC Motorhome
« on: September 28, 2016, 08:42:02 PM »
I always liked these GM motorhomes. I have never owned one or any type of motorhome for that matter. These seemed like the "Cadillac of Motorhomes" (even though they were actually built by the Pontiac Division) back in the 70's.

We went to my In-laws cabin about 200 miles from Vancouver and a neighbour of theirs had this parked out front so I couldn't resist gawking, taking pictures, Googling them etc.

I think that I read that the Mobile Radio was an option and this one came with one mounted front and centre on the dash between the two seats. It even has a blue GM sticker on the front of it.

These are front wheel drive so the floor in the motorhome can be low to the road and were built using the Oldsmobile Tornado / Cadillac Eldorado drivetrain. Of course the first thing I was trying to calculate was how much gas it would need in the tank to get it and its 400+ cubic inch Big Block V8 to the nearest gas station that is 20 miles away from where it is parked! Once I know that I can figure what a 1300 mile each direction trip from Vancouver to LALA land will cost.

Here is the basics from Wikipedia though there is much more to read about them on the Wikipedia site. The first one pictured in the WiKipedia article top right looks to be identical to this one!

https://en.wikipedia.org/wiki/GMC_motorhome

The GMC Motorhome was produced by the GM Truck & Coach Division for the 1973 through 1978 model years in Pontiac, Michigan, USA. It was the only complete motorhome built by a major auto/truck manufacturer, producing what GMC hoped would be their "halo" vehicle. Part of the reason this vehicle is so different from other motor homes of the era is that it was not conceived as just a "camper," but as a vehicle for comfortable travel as well. The design was radical for the day with front-wheel drive and a low profile, fully integrated body.
At the time (as now), motorhomes were built by recreational vehicle manufacturers on bare frames and drivetrains supplied by a chassis manufacturer. GMC built the bodies and in most cases the interiors in-house, and designed the chassis and drivetrain to create a motorhome enclosure that could be adapted to a range of purposes. Empty shells were supplied to other RV manufacturers for upfitting the interiors and also to specialty manufacturers for a range of custom purposes ranging from mail delivery and mobile training facilities to people movers and ambulances. It was built in 23 and 26 ft (7.0 and 7.9 m) lengths.


Terry
« Last Edit: September 29, 2016, 08:29:14 PM by AE_Collector »

Offline jsowers

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Re: GM Motorhome
« Reply #1 on: September 28, 2016, 10:36:58 PM »
Terry, if it helps your mileage figures any, my first car was an Olds Delta 88 with a 455 V8 and it got 15 miles to the gallon highway.  ;)  Of course the body was a little smaller than a motor home and the Olds only had one 25-gallon gas tank and the motor home has two.

I agree about those being the best looking motor homes ever made. Time does take its toll on mechanical things, though, so to keep it running might be expensive.
Jonathan

Offline AE_Collector

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Re: GMC Motorhome
« Reply #2 on: September 29, 2016, 08:27:48 PM »
Yes I too had a 15MPG City / 20MPG Hwy vehicle years ago. And that was Imperial Gallons not US Gallons! But it would really hit home to get 10 MPG (US) on a big trip in one of these now. Of course one gets used to prices after the shock wears off. Anyone on here who doesn't live in N America pays much more for fuel than we do. Even in Canada we pay considerably more than in the US.

Somewhere I read that while most other 40 year old motor homes are long gone, due to the way these were designed and built, if they are well maintained they are still very servicible. The whereabouts of close to 80% of them is known and most are still in service at least to some extent.

Some more about the GMC Motorhome from WikiPedia:

GMC motorhomes in good condition and in proper tune are as efficient as similarly powered modern motorhomes, despite the use of computer-controlled engines on the latter, and typically see 9 to 11 miles per US gallon (21 to 26 L/100 km; 11 to 13 mpg-imp) of regular unleaded fuel. GMC Motorhomes tested via a wind tunnel were reported to have a drag coefficient of 0.31, which is typical of modern sedans (although offset by the large frontal area).

The GMC motorhome enjoys one of the most active user groups of any brand of motorhome ever constructed. By a large margin, more GMC owners are members of the Family Motor Coach Association than any other vintage motorhome. The largest club of owners is GMC Motorhomes International, but about 20 other regional clubs are also active. Rallies are conducted frequently, with two GMCMI rallies per year attracting hundreds of GMC motorhomes.

Today the GMC motorhome has withstood the test of time and is being rediscovered by a new generation of recreational vehicle owners. The vehicle was built to allow flexible use of the interior, and thus is ideal for recycling for modern needs. Many are today adding new technologies to the drive train and suspension, satellite electronics, digital audio-video equipment, laminate floors, and new design upholstery and appliances to make what has been called the "26-foot, 12,000-pound antique hot rod with plumbing".

Several companies specialize in parts for GMC motorhomes, and the strong community has developed a substantial cottage industry for needed replacement and modernization parts. Most parts are still available from GMC or aftermarket suppliers who support muscle-car-era Oldsmobiles, or from suppliers dedicated to specialized GMC parts production.

« Last Edit: September 29, 2016, 08:32:47 PM by AE_Collector »

Offline HarrySmith

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Re: GMC Motorhome
« Reply #3 on: September 30, 2016, 09:12:15 PM »
I wonder if the phone works? It would be cool if they put Bluetooth in it. That was one of the things I planned to do in my Corvair when I had it.
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Offline andre_janew

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Re: GMC Motorhome
« Reply #4 on: October 01, 2016, 03:43:54 PM »
I think the "phone" may turn out to be a CB radio!

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Re: GMC Motorhome
« Reply #5 on: October 01, 2016, 07:01:12 PM »
It is a CB radio, model 130 "Messenger" series, made by E. F. Johnson, Inc.


Offline 19and41

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Re: GMC Motorhome
« Reply #6 on: October 05, 2016, 03:37:32 PM »
Does it use the Toro engine or the 501 from the Eldo?  I've always liked those too. 
"Any sufficiently advanced technology is indistinguishable from magic."
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Offline AE_Collector

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Re: GMC Motorhome
« Reply #7 on: October 05, 2016, 10:31:00 PM »
Looks like the 455 initially but later the 403 engine became a choice as well. Here is some more about the drivetrain from Wikipedia:

The motorhome had a front-wheel-drive transaxle, which GM called Unified Powerplant Package, originally used in the Oldsmobile Toronado and Cadillac Eldorado with an Oldsmobile 455 cu in (7.5 l) V8 from the Toronado, but the later models made use of the 403 cu in (6.6 l) V8. Both used the GM-designated Turbo-Hydramatic 425 automatic transmission, with a wide roller chain drive to connect the output of the longitudinally oriented engine to the transmission. The final drive was connected directly to the transmission, and power was fed to the front wheels using half-shafts that ran under the front portion of the engine. The engine was fueled with regular gasoline stored in two 25-US-gallon (95 l) tanks.

The GMC was equipped with front disc brakes and drums on all four rear wheels. A popular owner modification puts disc brakes on a pair, or sometimes all four rear wheels as well. The front-drive configuration eliminated the driveshaft and rear differential and solid axle found on most front-engined motorhomes. As a result, the floor could be designed only about 14 inches (36 cm) above the roadway. The low floor was too low for a rear cross axle, and GM designed the rear suspension as a tandem pair of wheels, mounted on bogies which rode on pins attached to the sides of the low-profile frame. With the exception of the wheel wells, the rear suspension does not intrude into the living space. The rear bogies are suspended using a double-ended convoluted air bag that is pressurized by an automatic leveling system to maintain the designed ride height. The leveling system can also be manually controlled to level the coach at a campsite. The overall chassis design, from the use of an existing GM E platform powertrain and a modified rear suspension has been considered an early ancestor of the crossover.
« Last Edit: October 05, 2016, 10:33:08 PM by AE_Collector »

Offline 19and41

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Re: GMC Motorhome
« Reply #8 on: October 06, 2016, 09:12:36 AM »
That's impressive to consider the power/drive system from an E body car was plenty to haul that RV.  Different times indeed!
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Offline Mr. Bones

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Re: GMC Motorhome
« Reply #9 on: October 08, 2016, 12:47:16 AM »
What was the top speed on these Big Bad Babygirls? Rear axle ratio(s)?

I'm guessin' there had to be some serious torque multiplication going on. Big ol' honkin V8's, but also BIG motorhome!

Dry weight?

Thanks, learnin' new thangs....

Best regards!
« Last Edit: October 22, 2016, 01:05:25 AM by Mr. Bones »
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Offline 19and41

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Re: GMC Motorhome
« Reply #10 on: October 08, 2016, 01:02:10 AM »
Apparently they were front wheel drive.  They used a turbo hydramatic transmission that was essentially folded in half with a belt drive coupling the two halves. then a diff driving the 2 CV's.
« Last Edit: October 08, 2016, 01:06:20 AM by 19and41 »
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Offline AE_Collector

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Re: GMC Motorhome
« Reply #11 on: October 08, 2016, 11:08:51 AM »
I was going to say that while there was a rear axle there was no "ratio" as it was front wheel drive. That is wrong though as there isn't a rear axle either. They kept the floor level very low by dumping the axle(s) and using bogeys for the wheels.

The weight of the completed motor homes was in the 11,000-12,000 pound area (5-6 short tons).

All in all, a very inovative design for the 70's in many different ways. Front wheel drive was one thing but with large block V8's, automatic transmission and dragging that sort of weight!

Terry
« Last Edit: October 08, 2016, 11:11:09 AM by AE_Collector »

Offline twocvbloke

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Re: GMC Motorhome
« Reply #12 on: October 08, 2016, 11:17:49 AM »
That's impressive to consider the power/drive system from an E body car was plenty to haul that RV.  Different times indeed!

Well, when you think about it, Cummins diesel engines often used in pickup trucks on that side of the pond power a lot of our buses over here, which are bigger & heavier than the pickups, but still get up and go quite easily... :)