The PD-4104 and PD-4106 were long-distance coaches of the GM old-look bus family, the series that Yellow Coach introduced in 1940 and that General Motors built for 29 years. The old-look name is an unofficial retronym applied to these buses after the New Look of 1959 arrived.
GMC PD-4104 at a glance
| Family | GM old-look transit and intercity bus |
|---|---|
| Introduced | 1940, with the Yellow Coach TG-3201 |
| Badge | Yellow Coach until 1944, then GM / GMC |
| Production | 1940 to 1969, about 38,000 buses |
| Construction | monocoque, not body-on-frame |
| Common length | 35 ft and 40 ft |
| Length range | 25 ft to 41 ft 6 in |
| Width | 96 in, or 102 in from 1948 |
| Engine | Detroit Diesel 6-71, or 4-71 in the shorter models |
| Transmission | Spicer angle-drive two-speed before 1948, Allison V-drive after |
| Air suspension | standard from 1953 |
| Air conditioning | available from 1958 |
Based on one source, the English Wikipedia article on the GM old-look bus family, of which the PD-4104 and PD-4106 are the PD-series coaches. No free photograph of exactly this model was found.
History of the GMC PD-4104
From Yellow Coach to GM
The old-look bus was introduced in 1940 by Yellow Coach with the TG-3201. Yellow Coach was an early bus builder partly owned by General Motors before being bought outright in 1943 and folded into the GM Truck Division to form the GM Truck & Coach Division. The Yellow Coach badge gave way to the GM nameplate in 1944. Production of most old-look models stopped when the New Look was released in 1959, but some of the smaller models stayed in production until 1969, and about 38,000 old-look buses were built over the 29-year run.
Design
The old-look bus was somewhat streamlined in appearance, resembling the PCC streetcar in styling, and its windows were smaller than those of later designs. Unlike most earlier buses it was built using a monocoque structure rather than a body on a frame, and it helped move the industry from petrol to diesel power. Most were powered by the Detroit Diesel 6-71 straight-six, with the four-cylinder 4-71 in the shorter models and petrol engines in some buses. Manual and automatic transmissions were offered: the Spicer angle-drive two-speed automatic before 1948 and the two-speed Allison V-drive afterwards, with a small number of electric-propulsion buses built in 1940 and 1942.
Comfort and model range
The old-look was available in several lengths from 25 feet to 41 feet 6 inches, although the most common were 35 and 40 feet. Most were 96 inches wide, with 102-inch models available from 1948. GM began offering its Thermo-matic heating and ventilation system in 1946 and started making suburban models in 1952, identifiable by larger passenger windows, high-backed forward-facing seats and optional luggage racks. From 1953 air-ride suspension was standard on all but the smallest models, and in 1958 air conditioning became an option.
The end of the old look
When GM introduced the New Look bus with its fishbowl front window in 1959, production stopped on all old-look buses except the second-generation models: the 28-foot TGH-3102, built until 1963, and the 30-foot 35xx models, built until 1969. The old-look design was also built abroad under licence, most notably in the Soviet Union as the ZIS-154, which was discontinued after little more than four years and 1,165 units.
Design and features
- Monocoque body: a stressed structure instead of a separate chassis and body.
- Diesel power: the Detroit Diesel 6-71 helped move transit buses off petrol.
- Streamlined shape: styling that echoed the PCC streetcar.
- Air suspension: standard on all but the smallest models from 1953.
- Suburban versions: larger windows, high-backed seats and luggage racks from 1952.
GMC PD-4104 versions
- TG-3201 (1940): the first Yellow Coach old-look bus.
- TDH-4512: a common 35-foot transit model of the family.
- PD-4104 and PD-4106: the PD-series coaches of the old-look family.
- Suburban models (from 1952): coach versions with high-backed seats and luggage racks.
- TGH-3102 and 35xx: the second-generation models built until 1963 and 1969.
The old-look coaches were replaced by the GMC New Look, and the intercity tradition continued with the Scenicruiser in 1954. More buses are in the GMC collection.
Sources
- GM “old-look” transit bus, English Wikipedia: history, design, transmissions, lengths, equipment, end of production
