The MC-5 35 foot coach was further developed into the very similar MC-5A and MC-5B. The MC-5C, MCI's last 35 foot coach for a long time, used the more modern MC-8 front end and was produced from 1977-1980. The MC-6 was an experimental 102" wide model of which only 100 were produced for Greyhound in 1969-1970. The MC-7, introduced in 1968, was MCI's first 40 foot 3-axle coach. This was replaced by the improved MC-8 in 1973 and the MC-9 in 1978. The MC-9 was to become MCI's best selling coach, with 9,513 built by MCI and TMC until 1990. The final MC model was the MC-12, a modernized MC-9, built on Greyhound request from 1992-1998 as the, for the time being, last 96" wide MCI model.
Demand for the MC-8 was such that a new production plant was established in Roswell, New Mexico, in 1973. Another reason for the establishment of the new plant were labor problems in the other plants around this time. The Roswell plant was incorporated as TMC, Transportation Manufacturing Corp. The MC-8 and MC-9 produced here were badged as TMC rather than MCI, but were otherwise similar to the Pembina/Winnipeg produced vehicles. Also produced in Roswell, from 1979 to 1982, was the TMC Citycruiser, a 30 foot transit model built under license from Orion. Later MCI coaches built in Roswell were simply badged as MCI.
In December 1986, Greyhound Corporation sold Greyhound Lines to an investor group but retained ownership of Greyhound Lines of Canada, MCI and TMC. This meant that the ties between MCI and its traditional largest customer and basically the founder of the MC range had been severed. In January 1987, Greyhound Corporation bought the GMC transit bus manufacturing, including RTS production in Pontiac, Michigan, and Classic production in Ste Eustache, Canada. The RTS production was transferred to the TMC Roswell facility, while the Classic production continued in Ste Eustache. An additional plant for the Classic was opened in New York State.
Several changes occurred during this period. TMC stopped production of coaches and concentrated on the RTS production in 1990. To avoid confusion between Greyhound Corporation and Greyhound Lines, which were now unrelated companies, Greyhound Corporation changed its name to Dial Corporation in 1991. In 1993 the Classic bus production was sold to Nova Bus. In August 1993, Dial Corporation divested itself from the bus production and established an independent corporation, MCII or Motor Coach Industries International. Included were MCI, TMC, Custom Coach Corp. and Hausman Bus Sales, among others.
In 1994, MCII merged with Dina from Mexico. As a result, RTS production and the Roswell plant were sold to Nova Bus, and MCI started marketing the Dina Viaggio coach in the US. Towards the year 2000 the integration of the two companies intensified and the new MCI F and G models are produced in Mexico.
While MCI is known for its coaches, the company has at various moments in its existence built transit buses, though those were normally not to MCI's own design.
More important was the production of the Orion I 30 ft transit bus in the TMC Roswell factory from 1979 through 1982. A total of 848 so-called TMC City Cruiser buses were built, mainly for various US transit companies. The model was virtually identical to the Orion built buses.
In 1987 MCI acquired General Motors' bus production which included both the RTS model in the US and the Classic model in Canada. The RTS production was moved to the TMC Roswell factory in New Mexico, where RTS production continued as the TMC RTS. Production of the Classic was continued as the MCI Classic in the existing facilities in Ste. Eustache, Quebec. MCI's only new development was the introduction of an articulated version of the MCI Classic in 1992. Only small numbers of this model were sold to Halifax and Quebec.
In 1993 the Canadian MCI transit bus factory was sold to Nova Bus, who continued the production of the Classic. The TMC RTS production facilities were sold to Nova Bus late in 1994, as a result of the MCI-DINA merger. Nova Bus continued the RTS production. As a result, both the RTS and Classic models have been produced by three different companies.