GM Buffalo bus

GM Buffalo bus is the slang term for several models of intercity motorcoaches built by the GM Truck and Coach Division of the General Motors Corporation at Pontiac, Michigan between 1966 and 1980.

History

Predecessors

=Scenicruiser=

The GM Buffalo bus models were strongly influenced by the PD-4501 Scenicruiser, produced by GM exclusively for Greyhound Lines between 1954 to 1956, in limited run.

The Scenicruiser was a split-level model, with a lower level at the front containing the driving console and 10 seats behind it, and upper level containing 33 seats. This also allows a baggage compartment underneath the second level, while providing 360-degree view for the upper level. A lavatory was located in the rear of the first level. Scenicruisers were equipped with an air-ride suspension utilizing air bags at each wheel, and were air conditioned. Later on, model PD-4106 a new design was incorporated, such as having air conditioning powered off the engine, a patented V-drive engine-transmission design, and the 8V71 Detroit diesel motor.

As Scenicruisers became a familiar sight around the United States and in advertising, competing bus companies including members of the National Trailways Bus System sought a vehicle to compete. One of the product designs developed in response to this market demand was the GM Buffalo bus. Unlike the scenicruiser, these models were available for sale to all operators, and in fact, Greyhound only purchased a few of them. Many features, such as the split-level design and the revision introduced in PD-4106 model, was included in the Buffalo bus.

Fishbowl transit and suburbans

The GM New Look Transit Coach series (nicknamed "fishbowl" for the six-piece rounded windshield) was introduced in 1959. In the early 1960s and later, thousands were built in the transit and suburban bus models. When designed and put introduction, the Buffalo intercity products shared many body and mechanical parts with these "fishbowl" buses, which were assembled in the same plant in Pontiac, Michigan.

This aspect, a sensible production economy at first, would negatively impact the future of the Buffalo models years later when GM switched transit production at the Pontiac plant to the modular RTS design, a radical change beginning in the late 1970s.

First buffalo models: GM PD-4107 and PD-4903

In 1966, GM introduced the PD-4107. Also known informally as "decks", these buses were similar in some ways to the Scenicruiser design, but had a a larger "second level" and the lavatory was located at the rear. The 4107 was convert|35|ft|m|sing=on in length, and nominally (without lavatory) would seat 41 passengers (38 or 39 with lavatory). In 1968, the PD-4903 was introduced, a convert|40|ft|m|sing=on long version of the 4107 which nominally would seat 49 passengers (46 or 47 with lavatory).

In the Buffalo design, the driver sat higher than in a Scenicruiser, but the passenger compartment was no higher than the Scenicruiser deck, so the Buffalo did not look like a double decker. The difference in the height of the front and rear roof was approximately one foot, giving a sleeker, more aerodynamic shape.

The products used an airplane-like stressed-skin construction in which an aluminum riveted skin supported the weight of the bus. The wooden floor kept the bus' shape. The engine cradle was hung off the back of the roof.

GM's Buffalo models were powered by the eight cylinder Detroit Diesel 71-series supercharged two-cycle diesel engines known as the 8V71. GM buses used a unique "V-drive" configuration with a transverse mounted engine. The transmission angled off at a 45-or-so degree angle to connect to the rear axle. The engines were canted backwards for maintenance access; in fact the only major components not accessible from outside the bus were the right-hand exhaust manifold and the starter. The entire engine-transmission-radiator assembly was mounted on a cradle that could be quickly removed and replaced, allowing the bus to return to service rapidly, leaving the powertrain in the shop for repairs. The original transmissions were a 4-speed non-synchronized manual transmission with solenoid reverse. Late in production, an Allison automatic version was offered.

The 4107 and 4903 models were notorious for being difficult to shift gears, routinely making loud, grinding noises which tended to upset the passengers. Double-clutching reduced these embarrassing noises, but even the most skilled driver would occasionally have problems, especially when changing buses (or powertrains) meant an unfamiliar feel to clutch and shifter.

econd generation: GM PD-4108 and PD-4905

In 1970, design improvements came with the updated versions, PD-4108 (35 ft) and PD-4903 (40 ft). The 4108s drove ran a lot stronger than 4107s and the drivers controls updated, as they were with the 4905. These second generation Buffalo models came with a synchronized transmission, like a car, but they were still quite difficult to shift. If you tried to shift them like a normal bus, you had to shift them very fast. The biggest gripe about the 4905, from the drivers' point of view, was that the extra convert|5|ft|m of length was all between the front and rear axles. It was very easy to scrape the baggage bins on tight turns. The 4905s looked just like 4108s but with 3 baggage bins. Some 4905s had a tag axle, with a single extra wheel on each side, located in the third baggage bin, but it was forward of the drive axle, so turning radius was not affected.

Additional updates in models

In 1972, the PD-4108 was redesignated P8M4108, and the PD-4905 became P8M4905. In 1979 and 1980, the P8M4905 was replaced with the short-lived model H8H649.

Markets

The GM Buffalo models were purchased primarily by affiliates of the National Trailways Bus System and many smaller operators. After the Scenicruiser arrangement with GM, Greyhound had purchased an interest in Canadian bus manufacturer Motor Coach Industries (MCI), and by the mid-1960s, had switched most of its purchasing to MCI products. In the 1970s, MCI products began to overtake the GM Buffalo models in sales volumes, especially after the introduction of the popular MC-8 at the Transpo 72 exhibition held at Dulles Airport near Washington, DC in 1972.

As the market share declined, GM lost interest in updating its motorcoach products. When the GM RTS bus models replaced the fishbowl models in GM's transit bus offerings, the future discontinuation of the Buffalo models, which shared many common parts with the fishbowl, was sealed. The final Buffalo models were built in 1980.

ee also

*GM PD-4501 Scenicruiser
*GM New Look Transit Coach
*Rapid Transit Series - next transit generation bus
*GMC Classic bus

References

External links

* [http://www.scenicruiser.com Scenicruiser home page]
* [http://www.strayhound.com/traveler.htm The original Scenicruiser]
* [http://busexplorer.com/PHP/MidPage.php?id=173] [http://busexplorer.com/PHP/MidPage.php?id=181] [http://busexplorer.com/PHP/MidPage.php?id=2441] Images of Buffalo Bus