Bus Stop Classic: GM PD 4107/4108 and 4903/4905; GM’s Buffalo – Last Of The Line


cc-72-142(curbside shots by PN)

(first posted 10/15/2016)     There are highs and there are lows…that old adage certainly sums up GM’s long history of intercity coach manufacturing.  From the highs of the 1940’s, to its peak in the 50’s, to the parity of the 60’s and then the decline in the 70’s – let’s take a look at the last intercity models to come down the Truck and Coach assembly line in Pontiac Michigan – the GM “Buffalo” series…


For our non-bus fan readers, you may be curious as to how the model acquired this nick-name.  Think of a buffalo, with its shoulders higher than its head and neck – the 4107/4903 with its higher raised floor and lower front driver’s area could be considered somewhat similar looking.


Next, a little history. The GM PD 4104 “Highway Traveler”, produced from 1953 –1960, was a  major leap in technology and innovation – the first intercity bus with full alloy monocoque construction, air suspension, and large slanted picture windows – it was leagues ahead of any of its competitors, established the standard for the modern 35′ coach, and was a huge success for the company.


The PD 4106 followed, built from 1961 to 1965.  It was essentially an updated 4104, with some stylistic changes, larger windows, and powered by the recently introduced 8V-71 diesel, which allowed a new efficient combined heating and cooling system, with the compressor driven off the engine rather than a smaller auxiliary motor.




Eagle Model 05

So what to do next?  Well, transit operators were looking for larger coaches – ones with more under floor storage space and in lengths greater than 35 ft.  At this same time, Greyhound was transitioning to an all MCI fleet, and Trailways was committed to its Eagle brand coaches.  GM looked at the remainder of the market and decided that to be competitive, it needed to field a bus in both 35 and 40 ft lengths, but with a raised floor to offer competitive underfloor storage.


While the PD 4501 Scenicruiser had a series of mechanical and structural issues that caused Greyhound headaches, from a marketing and publicity perspective, these and GM’s other coaches were hugely successful.  My guess is GM thought it could leverage some of this Scenicruiser “brand value” and that led engineers and stylists in the direction of a bi-level, stepped design.


Of course it was also just expedient, as the whole front end was essentially identical to the 4106, and the rear just elevated. In 1966, GM introduced the PD 4107; P = Parlor (the name used since the 1930’s to designate a highway coach) D = Diesel, 41 = Typical Passenger Load (depending on whether lavatory installed), 07 = Model No.  The 4107 was a 35 ft bus, somewhat similar in looks to the PD 4501 Scenicruiser, but without the front low seating area and restroom. Rather than having 5 rows of seats on a lower level behind the driver, the 4017 had three stepped rows, each having 4 seats, going from the driver’s area to the upper floor, similar to stadium seating.


In 1968, the PD 4903 debuted joining the 4107, with an extra five feet spliced into the bodywork between the front and rear wheels – making a 40 ft coach.  The 4903 also introduced a 24 volt electrical system, the first on any bus.


Both versions used GM’s 8V-71 engine, arranged in a “V“ drive configuration.  Transmission was a 4 spd Spicer unit.  Overall, these buses enjoyed a good reputation; they exhibited GM’s excellent build quality at the time and the extended wheelbase 40 ft models rode very smoothly.


My research turned up only two criticisms; they were notoriously rough shifters – the non-synchronized Spicer box required double clutching, and even then gears tended to grind.  And while the extended wheelbase gave a smooth ride, it made for a low bus that would often bottom-out or scrape its undercarriage on uneven roads and while leaning in turns.


Greyhound purchased 162 4107’s in 1966, and a further 200 in 1967 – but with MCI production capacity now able to meet its demands, these would be the last GM coaches the company would procure – thus ending a storied 30 year partnership.  The bus in the picture above, No. 5028, was the last one delivered to Greyhound.


Minor updates, a synchronized Spicer transmission and improved driver’s area, came in 1970 with the PD 4108 (35 ft) and 4905 (40 ft).  Even with the new transmission, driver’s continued to complain about shift quality.


A tag axle could be added to the third luggage bay of the 4905 for those states with lower axle loading laws. It should be noted that the 4905 was the only American 40′ coach that didn’t require a third axle in many/most states; the other 40 footers all had two axles in the rear. GM’s design and construction made for the lightest coach in the industry.


Throughout the 1970’s, sales gradually dwindled.  In 1972, GM changed the model designations from PD 4108 and 4905 to P8M 4108A and 4905A, respectively – equivalent to its transit coach naming convention.  Then finally in 1979, the 4905 was renamed H8H 649.  An Allison automatic transmission was available on these last two years of production.  The final Buffalo produced, No. 233 pictured above, was delivered to California-based Eastshore Lines in 1980.


So, what’s the overall verdict?  My take is the Buffalo clearly wasn’t a bad bus – it was just not the definitive segment leader its predecessors were.  Its contemporaries, the MCI 7/8, and Eagle 05/08, were equal, if not better than the Buffalo.  Also sealing its fate was the sharing of some manufacturing techniques and components with the New Look transit coach.  The New Look ceased production (in the US) in 1976, supplanted by the RTS II which used a new modular construction process.  With its sales decreasing yearly and no longer able to spread production costs across two platforms, post 1976, the Buffalo was living on borrowed time.


Total Buffalo production over 14 years was 4530 coaches – quite a few can still be seen on the road today as motor home conversions.