AUTO THEFT is on the rise, and it's taken a new turn. Kids used to steal cars to take joy rides, and 90 percent of those cars were eventually returned to owners. Now professional thieves are stealing cars to order so that the parts can be sold separately. Only 55 percent of the million cars stolen in 1980 were recovered. Stolen cars are brought to back-alley workyards--they're called "chop shops"--where two men can completely dismantle a car in 40 minutes. Then the component parts are ready for resale. A door in good condition can bring $300, a front end assembly up to $2,000.

Two major parts--the engine and the transmission--are hardly ever resold though, because, by law, they are required to be marked by the manufacturer with an individual vehicle identification number. The identifying number makes the part harder to sell and easier to trace.

Rep. William Green (R-N.Y.) and Sen. Charles Percy (R-Ill.) have proposed that this identification system be extended. They want manufacturers to put the numbers on 14 other major auto parts, a step they believe would discourage theft, aid lawmen in identifying stolen property and help prosecutors convict thieves. Their bill has widespread support among consumer and law enforcement organizations, and the insurance industry and legitimate auto dismantlers and recyclers are behind it, too.

Justice Department officials had expressed support, but earlier this year the official administration position was announced by the Department of Transportation. The administration said it opposes the bill because adoption of the identification system would "cost too much" and would be an added burden on the beleaguered automobile industry.

This is a weak argument in light of the fact that pilot programs undertaken by Ford and GM added only $3 to $5 to the cost of every car. At most, supporters of the bill say, the new system could cost $10 a car. That seems a small price to pay for a simple and effective deterrent to crime.