General Motors Corp. yesterday announced a voluntary recall of 3.1 million mid-size cars because some may have defective rear axles that could break down while the cars are in motion.

The recall is one of the largest in the history of the National Highway Traffic Safety Administration, which was set up in 1966 to police manufacturer compliance with government auto safety standards.

The largest auto recall involved 6 million Chevrolet cars made by GM for the 1972 and 1973 model years. Those cars were brought back for inspection of possibly faulty engine mounts.

The axle-inspection program announced by GM yesterday affects many 1978- through 1980-model Chevrolet Malibu and Monte Carlo passenger cars and El Camino sedan pickups. Other affected passenger cars for the same model years include the Pontiac LeMans and Grand Prix, the Oldsmobile Cutlass and Cutlass Supreme, and the Buick Century and Regal. The GMC Caballero, another sedan pickup -- a vehicle with a passenger-car front end and a truck flatbed -- also is included in the roundup.

Most of the vehicles in the new GM recall have rear axles that were manufactured at a GM parts plant in Buffalo, N.Y. All of the vehicles involved have rear-wheel drive.

GM produced 5.3 million mid-size cars for the 1978 through 1980 model years. But the rear axles in about 2.2 million of those models were made at plants in Michigan and Canada, GM officials said.

NHTSA said in a consumer warning issued in April 1983 that the axle defect could lead to loss of driver control, "injuries, death, or property damage."

However, neither NHTSA nor GM yesterday reported any deaths stemming from rear-axle-related accidents. GM said that the cars in question have been driven more than 200 billion miles "with their rear axle subassemblies demonstrating a reliability rate of 99.98 percent."

Over the five to seven years that the cars have been on the road, there have been reports of 200 axle separations involving 15 injuries, GM officials said.

GM last year disputed NHTSA's consumer warning and argued that no recall of the 1978-1980 mid-size cars was warranted. The issue then was complicated by the release of a NHTSA film purporting to show the rear wheels falling off a 1979 Malibu station wagon as the result of axle failure.

The filmed event was staged -- a legitimate practice used to demonstrate the possible consequences of a defect. But NHTSA failed to identify the staged breakdown as a simulation at the time it was presented.

GM yesterday reiterated its contention that NHTSA's airing of the film was unfair to the company. "There is near-universal agreement that the agency erred by not disclosing that it had removed parts from the car to induce the separation, leaving the impression that it was a frequent or commonplace event," the company said.

GM agreed to recall the 1978- through 1980-model mid-size cars "when we found that the axles from the Buffalo plant had a slightly higher abnormal wear and/or axle failure rate," a GM spokesman said. "We could not ignore that."

GM officials believe that the axle defect is caused by an improperly hardened part, called an end button, in the rear-axle shaft and wheel assembly. The button may be too soft, causing it to wear excessively. That, in turn, could lead to the loss of a "C" clip that helps to hold the axle in place. Loss of the clip could lead to the separation of the axle and rear-wheel assembly from the car body.

An initial indication of the condition is excessive rear-axle play, which causes a kind of fishtailing motion of the car's rear end, according to NHTSA officials.

According to some industry estimates, GM could spend as much as $125 million repairing the cars. A fix could involve anything from an axle adjustment to replacement of the full rear-axle subassembly, GM officials said.