GM Buffalo bus
|GM Buffalo bus|
|Manufacturer||GM Truck and Coach Division (General Motors)|
|Body and chassis|
|Floor type||step entrance|
GM Buffalo bus is the slang term for several models of intercity motorcoaches built by the GM Truck and Coach Division at Pontiac, Michigan, between 1966 and 1980. "Buffalo" buses have a stepped roof in front, and the first three rows of seats are at different levels, mounted on stepped floors similar to some theatre seating.
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 allowed 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, having air-conditioning powered off the engine, a patented V-drive engine-transmission design, and the 6V71 or 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; the last GM bus purchased by Greyhound was a 1967 PD4107. Many features, such as the split-level design, and the revisions introduced in the PD-4106 model were 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 into production, 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 have a negative impact on 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 larger "second level" with the first level reduced, and the lavatory was located at the rear. The 4107 was 35-foot (11 m) in length, and nominally (without lavatory) would seat 41 passengers (38 or 39 with lavatory). In 1968, the PD-4903 was introduced, a 40-foot (12 m) long version of the 4107 which nominally would seat 49 passengers (46 or 47 with lavatory). The PD-4903 was the first GM bus to use a 24 volt electrical system and was 40 feet long with a third luggage bay. For states with lower axle load limits, a factory option used the third bay to hold a retractable two-tire axle.
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 left hand rotating 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, which were accessible from underneath and through access panels under the rear bench seat. 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.
Second generation: GM PD-4108 and PD-4905
In 1970, design improvements came with the updated versions, PD-4108 (35 ft) and PD-4905 (40 ft) both with a 24-volt electrical system. The driver's controls were updated for both. The biggest gripe about the 4905 and 4903, from the drivers’ point of view, was that the extra 5 feet (1.5 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 three 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 P8M4108A, and the PD-4905 became P8M4905A. In 1979 and 1980, the P8M4905A was replaced with the short-lived model H8H649.
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.
Total production for 35-foot models was: PD-4107 1,267 (1966-69), PD-4108 65 (1970-71), PD-4108A 232 (1972-79); and for 40-foot models was: PD-4903 401 (1968-69), PD-4905 330 (1970-71), P8M-4905A 2,002 (1972-79), H8H-649A 233 (1979-80).
- GM PD-4501 Scenicruiser
- GM New Look Transit Coach
- Rapid Transit Series - next transit generation bus
- GMC Classic bus
- GM PD-4103
- List of buses
|This does not cite any references or sources. (January 2007)|