The Flxible division of the Rohr Corp. submitted a low bid of $7,377,135 yesterday for the construction and delivery of 100 new transit buses for the Washington Metrobus system.

Rohr, the parent company, is the builder of the rail cars for the Metro subway. Its Flxible subsideary is located at Loudonville, Ohio. The firm supplied 145 buses to Metro last year.

With its bid, which totals $66,406 per vehicle, Flxible apparently defeated its only competitor, the AM General Corp., which set a total price of $7,912,805. AM General supplied 620 buses in 1975 that Metro officials have described as lemons.

Flxible also bid $762,831, or $74,628 per vehicle, for a related order of 10 suburban model buses designed for longer-high-speed routes. AM General's price was $857,643.

The General Motors Corp., the nation's largest bus supplier, did not bid because it is converting to a new model vehicle that does not meet Metro's specifications, if told Metro in a telegram.

The contract for the new buses will be awarded by the Metro board after the bids are officially certified. The U.S. government will pay 80 per cent of the cost under its mass transportation program.