Bus Stop Classic: GMC PD-4501 Greyhound Scenicruiser – Everybody’s Favorite Bus Except For Greyhound And GM

(first posted 12/24/2013)     How did the Scenicruiser become such an icon, undoubtedly the most-recognized bus ever built in the US? It’s safe to say that after the Scenicruiser made such an indelible impression on Americans in the fifties and sixties, every other bus was just…a bus. After a protracted wait to see what the industry would come up with as the definitive new bus of the post-war era, the Scenicruiser arrived in 1954 as the herald of a new era, one that would redefine the genre and make riding the bus exciting again. Yes, the bar was set  high, but the Scenicruiser failed to clear it, despite the legacy of its instantly recognizable shape.

Yellow Coach 719 1937

In 1936, GM’s Yellow Coach Division set the template for the modern American intercity bus with its Model 719 Super Coach: forward control, high floor with ample luggage space below, semi-monocoque construction including the use of aluminum alloys, air conditioning, and a rear-mounted engine (gasoline, at that stage).  At the time there were many small independent bus manufacturers, and with the Model 719, GM began its climb to dominance in the field.

CC 121 096

By the time its replacement arrived in 1940, the PD-3751 “Silversides” (CC here), GM’s ground-breaking two-stroke Detroit Diesel engine was in full production (Birth of the DD engine here).  The DD 6-71 engine was compact, efficient, light and powerful (some 165 hp in its early versions), the perfect engine to propel buses into the diesel age. Its size allowed it to be mounted transversely at the very back of the coach, maximizing space efficiency. Since GM wouldn’t sell its diesels to its bus-making competitors–until forced to as a result of a 1956 anti-trust lawsuit–GM’s buses enjoyed a very distinct competitive advantage. This pre-war Silverside design, built exclusively for Greyhound, and its many other variations became the dominant bus of the immediate post war era.

Loewy greyhound

Greyhound had also become the dominant nationwide interstate bus carrier already well before before the war, and there was considerable anticipation as to what the Greyhound bus of the future would be. In 1945, GM and Consolidated Vultee were each given development contracts for a post-war bus, but by 1946 both cancelled their contracts due to too much other work. They turned over their blueprints to Greyhound, which then went it alone, commissioning  Raymond Loewy to do the styling on a 50 passenger bi-level coach dubbed the “Highway Traveler”.

Greyhound GX-1

The GX-1 Highway Traveler was built in 1947 at Greyhound’s own repair and maintenance shops. It seated 37 passengers on the upper level and 13 below. The GX-1 was 35 feet long, then the maximum length allowed by virtually all states. That was the particular appeal of the bi-level arrangement, the only way to increase passenger seats within that limit. The GX-1 also featured a primitive version of air suspension.

The biggest challenge was finding a suitable power plant that would both be able to propel the tall and heavy coach at decent speeds up long grades as well as be economical on the flats. Powerful gasoline engines like the Hall-Scott had the first part of the brief covered, but were exceedingly thirsty. The DD 6-71 just wasn’t powerful enough, and there were no larger versions of the DD family back then. That led Greyhound to an unusual solution: twin air-cooled V6 engines from the Aircooled Motors Co., the successor to Franklin Motors and the source of the Tucker’s aircooled six. The original idea was that both engines would run on the hilly sections, and then one engine could be shut down on the flats.

Here’s some unedited footage shot of the GX-1’s presentation. The Greyhound executives are obviously proud of their new bus, but in reality, the GX-1 had a number of issues with that unusual drive train, as well as others. Greyhound was pioneering new ground, and it it wasn’t smooth going.

Greyhound GX-1 ad

The GX-1 had a brief career in revenue service, but it was soon sidelined at the Greyhound shops where it had been built.

Greyhound GX-1 shop

There it sat under a tarp, until it was finally scrapped in about 1955 or so. Time for Plan B.

The next version, the GX-2 prototype, was named “Scenicruiser”, and was a considerable departure from the GX-1. Although again styled by Loewy and built by Greyhound, this time GM Coach was much more involved in its design, development, and even its styling.

Scenicruiser prototype afrom a children’s book that I used to read to our kids

 Although the Scenicruiser would be exclusive to Greyhound, GM was in the early development of its next generation 35′ coach, and wanted to reap efficiencies from both projects.


Greyhound GX-2

GM even sent an unfinished 35′ PD-4151 bus shell to Greyhound, a starting point from which they created the 40′ dual rear-axle GX-2 Scenicruiser prototype. The Scenicruiser’s split-level configuration, with ten seats and the lavatory on the lower front compartment, and the additional 33 seats in the higher rear section allowed a very large luggage compartment under the raised section, and was generally a more practical configuration than the bi-level GX-2. But there was one big hurdle; or many actually.

The 1949 GX-2 was 40′ long, and almost all states had still had that 35′ maximum length restriction. Greyhound used the GX-2 to lobby for increasing that limit, a process that took several years. The film in this video was shot by the Oregon State Police, the GX-2 presumably showing off its maneuverability as part of that process that took several years.

Pickwick 1928 Cherokee 001 1200

Let’s take a brief diversion back, to consider the Scencruiser’s distinctive split-level design. It was hardly new or innovative; the oldest bus I can come up with that used a similar approach is this 1928 Pickwick Cherokee, which also placed the driver up high in his own compartment.

Bus Kenworth 1937 bus

This 1937 Kenworth is even further along in the direction of the Scenicruiser. It used an under-floor lay-down engine, probably a Hall-Scott.

Trailways Brill a

And this Brill built for Continental Trailways shortly after the war makes it clear that Lowey’s claim to have “invented” the Scenicruiser rather without merit. It was a 35 footer, and not successful.

Greyhound GX-2 Prototype

In addition to the length restrictions, there was another hurdle to jump with the GX-2, the same one that the GX-1 had failed to clear: a suitable power plant. The prototype GX-2 used the DD 6-71, now up to some 200 hp, but it just wasn’t going to be up to the task of a fully loaded 40′ bus. GM used the GX-2’s limited revenue service to experiment with various solutions to soup up the 6-71. Different cylinder liners with bigger ports, high lift cams, and a higher operating engine speed were tried, but not considered satisfactory. A two-speed auxiliary transmission helped a bit further. The GX-2 was just underpowered.

Next: the production Scenicruiser:

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