Washington Metro's bus problems have not been as spectacular as New York's, but they have been persistent and expensive and have included structural defects and major problems with engines and transmissions.

Metro has no Grumman Flxible Model 870s, the new bus that has been bringing grief to New York City and 26 other transit operations in the United States. Metro's 115 newest buses, the dark-windowed ones that are similar in appearance to the Flxible 870, are from General Motors and are known as the RTS.

However, Metro's active fleet of 1,767 buses includes 564 older-model Flxibles, including the last 281 buses Flxible made before it switched to the Model 870. Some of those buses, in service at least since 1978, have developed cracks in the engine cradle (the metal frame that holds the engine) and in the wheel suspension areas. The cracks can be repaired with welding, according to Metrobus maintenance chief Phil Price. There is no safety issue, he said.

The big problem for Price, and one that forced him to seek a $1.5 million increase in his maintenance budget for this year, has been the reliability of engines and transmissions on both the new GM buses and the 281 Flxibles. The blame goes to General Motors, because GM subsidiary Detroit Diesel Allison builds the engines and transmissions for Flxible as well as itself.

"We used to get 200,000 miles between breakdowns on bus transmissions," Price said. "Now we are getting 30,000. It got so bad that we would fix a transmission, put it out on the street, and in some cases not get six blocks out of it."

E. r. Stokel, director of public transportation for GM, said that GM has reworked the transmission, extended the warranty on it for one year and paid a number of the bills. "I'm satisfied that this transmission will provide the same kind of life Phil had been getting in the past," Stokel said.

Before Price accepted the RTS buses, he checked with purchasers of the first RTS models and developed a list of 42 problems he asked GM to solve before Metro took delivery. Price praised GM's response and, like other maintenance chiefs interviewed, feels the RTS will become the standard that other bus manufacturers must meet.

However, Metro General Manager Richard S. Page said in an interview that he is reconsidering his earlier plans to buy more buses from either GM or Flxible until he is confident Flxible has solved its troubles with the Model 870.Flxible intends to compete for Metro's next bus contract, Flxible officials said. Page, meanwhile, is considering a major program to rebuild old buses rather than buy new ones.

Metro's fleet of 610 AM General buses, which the transit authority purchased shortly after it took over the operation of the area's bus system in 1973, was plagued with troubles, including inadequate air conditioning and cracks in the frame around the wheel. Those problems have been solved and the AM General buses are running well, but that success came only after a long struggle.

Price, who has more than 30 years in the bus business, is philosophical about the problems. "Every new bus I've ever seen has had trouble that has taken time to fix," he said.