General Motors announced yesterday that it will not bid of transburg, the Department of Transportation's much-South-After low-floor bus that is suppose to make bus riding easy for the elderly and for wheelchair-bound hill.

That means that when the bids are opened Wednesday on 530 new buses for Los Angeles, Miami and Philadelphia, no United States manufacturer will be bidding. Grumman flexible, the other possible Americanfirm, pulled out of the competition March 11. In fact, Federal officials say they do not know if any foreign firms will bid, although several have expressed interest in the specifications.

In a letter to transportation Secretary Brock Adams, GM vice president Robert W. Truxell cited "major engineering, operating and performance concerns" in the federally mandated Transbus specifications. "Transbus vehicle design represents far too great a risk for us to develop and produce," Truxell said.

Adams, in a statement, said, "it is extremely disappointing to hear American industry tell the elderly and the handicapped that it will not build the bus of the future that can and should be produced in this country."

Both GM and Grumman Flxible have successfully sold new-look buses to transit authorities. DOT officials have claimed privately that GM and Flxible were more interested in recovering development cost on those "interim-design" buses than in attempting Transbus. Both firms have denied that charge and have cited difficulties they had with the federal specifications.