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GM Bus Model Numbers and Codes

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This page was last updated on September 9, 2016.

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GM Model Numbers and Codes

The model designations used for GM buses consisted of a series of two or three letters followed by a series of four numbers (for example, TDH-4512). The letters and numbers gave a basic description of the type of bus as follows:

P D H 37 51 M    
| | | | | |    
| | | | | > Special Code:
| | | | |     A - Air Conditioned
| | | | |     M - (?? 1939-1942, 1944 only)
| | | | |     N - No Air Conditioning (after 1968)
| | | | > -- Series:
| | | |       (sequencial number, Series 01, Series 02, Series 03, etc.)
| | | > -- -- Number of Seats:
| | |         (Parlor: 25, 29, 33, 37, 41, 45, 49)
| | |         (Old Look: 27, 31, 32, 35, 36, 37, 40, 45, 48, 51, 54, 55)
| | |         (New Look: 33, 45, 53)
| | > -- -- -- Transmission or Special Code:
| |           (not used prior to 1947, except on electric vehicles)
| |           E - Electric
| |           G - Greyhound-only design
| |           H - Hydraulic
| |           M - Mechanical
| > -- -- -- -- Fuel:
|             D - Diesel (until 1968)
|             G - Gasoline (until 1968)
|             6 - 6-Cylinder Detroit Diesel Model 71 (6V71) (after 1968)
|             8 - 8-Cylinder Detroit Diesel Model 71 (8V71) (after 1968)
> -- -- -- -- -- Type:
              P - Parlor (Intercity)
              S - Suburban
              T - Transit

Andre Kristopans wrote on September 9, 2016:

Originally (1939 thru 1948) coding was as follows:

  • 1st letter - type (T - transit, P - parlor)
  • 2nd letter - fuel (G - gasoline, D - diesel)(DE in a couple of models designated Diesel-electric, i.e. in modern terminology, a "hybrid")
  • first two numbers - nominal seating capacity (21 thru 55). Actual seating capacity frequently was smaller, as nominal seating capacity was based on minimum seat spacing.
  • final two numbers - series. Not all series numbers were assigned. For instance, there were no TD4504's as all series were changed to end in "05" in 1941.

In 1948 GM decided to add a third letter to the model number, designating transmission type, M for manual, H for Hydraulic. This change was made during production of the 3207/3610/4008/4507 types. Originally the hydraulic transmission versions were supposed to be 3208/3611/4009/4508 and the manual transmission versions keeping 3207/3610/4008/4507. Note that most of these had already been produced with hydraulic transmissions!

The next big change came in 1968 when the designations for the 45 and 53 seat buses were changed with the D for Diesel changed to 6 or 8 designating number of engine cylinders. A suffix A was added designating buses with air conditioning, which were now placed in a separate serial sequence. Previously they had been intermixed with non-air-conditioned versions. The small 35-seat and later 33-seat buses still were designated G or D as a second letter, as they were still available with gas engines.

In 1972 the a/c and non-a/c versions were again put into a common sequence, with N designating non-air-conditioned buses.

With the start of RTS production, the designations were initially changed again. T designated Transit, second letter type of engine (W = 6 cylinder, H = 8 cylinder, J= 6 cylinder turbocharged), first number length (7 = 35 foot or 7 modules, 8 = 40 foot or 8 modules), second number width (6 = 96", 2 = 102 "), last two numbers series. Note series 02 never existed.

During series 03, the order was shuffled a bit. instead of TW7603 it became T7W603, but meaning did not change. At start of series 04, the engine type letter was dropped, replaced by a "0", so that T7W603 becomes T70604.

Series 05 was a single transverse-engine experimental, series 07 was a pair of transverse-engine experimentals. Series 8 was a major redesign putting the wheelchair lift in the front door instead of the rear door.

Nova totally changed designations, and got somewhat messy doing so. What had been a series 6 became "T802NFD" (for Narrow Front Door) while series 8 became "T802WFD" (Wide Front Door). 30-foot buses were introduced, as T602NFD or T602WFD. 35-footers became T702NFD and T702WFD. 96-inch wide buses were apparently discontinued by Nova. Towards the end many buses had mis-stamped plates, with just the T802, etc on them. It is believed these were not official changes, but rather the results of poor communication within the organization.

A note on parlor buses: their designations basically followed the changes in transit bus designations, with a few differences. Prewar 37 and 41 seat parlors had special models designated PDG or PGG built to Greyhound specifications, while PGA and PDA designated buses with air conditioning, all built again for Greyhound.

The PGA3301 was a Korean War special built for the military, with a transit front grafted onto a parlor-type body.

In 1979 the P8M4905A was redesignated a H8H649, which translated into H - High Value, 8 - 8 sections or 40-foot, H - hydraulic transmission, 6 - 96", 49- 49 nominal seating. However, this model designation was not always accurate, as some had mechanical transmissions, just as some P8M4905A's had had hydraulic transmissions.

More Information

GM/Yellow Coach "Old Look" Buses at Wikipedia -- Wikipedia article about GM's "Old Look" buses, manufactured from 1940 through the early 1960s.

GM "New Look" Buses at Wikipedia -- Wikipedia article about GM's "New Look" buses, manufactured from 1959 through 1986.

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