The GM 51's were one of the best-built and most reliable buses even to
roll off an assembly line came from GM in the 1950s. The whole decade might be
regarded as GM's high point in the bus field. The first of the "standardized"
GM 51-passenger diesels went into production in 1950. This was the TDH-5103
model and it was 102" wide. 950 TDH-5103 buses were built between July 1950
and June 1953 for 13 properties, the biggest Customer was Pacific Electric Lines
Co. with 190 coaches. Also, 37 TDM-5103 buses with manual transmission
were built for Pacific Greyhound Lines. The TDH-5103 model was replaced in the
middle of 1953 by the TDH-5105 which had air suspension but was otherwise
identical to the 5103. It became the standard big-city transit bus of the 1950s.
Hundreds of streetcars and trolley coaches were replaced by 5105s, at total, 3,631
coaches were built by GM between May 1953 and June 1959.
GM Coach TDH-5103 demonstrator, produced in July 1950, was sent to the New
York area during the month followed and was tested by most of the NYC operators.
Buses wider than 96 inches were not allowed in the state then, so narrower model
TDH-5104 was produced by GM. 162 buses were built between September 1952
and September 1953. Air-suspension model TDH-5106 was introduced in August
1953; 1,727 buses were built at total.
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