Faulty 604 transmission is a project for a specialist

The streets of Beverly Hills are full of late-model BMWs, Mercedes-Benzes, Lexuses and Bentleys, but not too many 1990 Chrysler LeBarons.

That doesn’t bother Dennis Gewant, a Beverly Hills businessman and stalwart lover of the LeBaron convertible. The LeBaron model was produced for about 20 years starting in the mid-1970s.

Among mechanics, however, the LeBaron is famous for its 604 automatic transmission, which also had been installed in Chrysler minivans.

The 604 has a long history. Internet sites are full of postings by LeBaron owners who have struggled with repeated 604 failures. Chrysler has issued dozens of technical service bulletins to address problems with the transmission, according to Alldata, an Elk Grove, Calif., company that publishes bulletins for the auto repair industry.

“The Chrysler 604 is probably one of the worst transmissions in the world,” said Sam Memmolo, a master technician in Georgia and a nationally recognized car maintenance expert.

Gewant, a former New York City banker who runs a candle store on Rodeo Drive, knows the pitfalls of the four-speed 604 gearbox. The mechanics at Buerge Chrysler Jeep in West Los Angeles first began working on Gewant’s beloved LeBaron two years ago when he complained it would shift to a lower gear without warning and for no reason. The abrupt downshift would cause the car to lurch and the front end to nose-dive.

Gewant’s LeBaron isn’t exactly what you’d call a collector’s item. Kelley Blue Book lists the car’s trade-in value at a little more than $2,000. Nonetheless, Gewant loves the car and protects it with a Lojack antitheft device.

Buerge put a new transmission in the vehicle, which did not solve the problem, Gewant said. The mechanics concluded that the replacement transmission had the same defect as the original, and about three months later put a third transmission in the vehicle. That too was replaced by a fourth just a few thousand miles later.

“Nobody should have to put up with this,” Gewant said.

In fact, many people do put up with such headaches when it comes to complex, electronically controlled systems in their cars. All too often, mechanics repeatedly replace parts on cars because it is impossible to tear down and diagnose complex systems that are interrelated.

Lance Wiggins, the technical director at the Automatic Transmission Rebuilders Assn., a national trade group that represents transmission shops and remanufacturing plants, said the 604 is a major source of business for independent shops.

“Our shops rebuild more 604s than anything else,” he said.

Wiggins said electronically controlled transmissions such as the 604 need specialty transmission mechanics, who often are not part of a dealership’s staff.

Gewant’s 604 transmission abruptly downshifts when he touches his foot to the brake. He considers it a major safety problem, but it occurs sporadically and often disappears in the presence of mechanics.

Gewant has taken the car to numerous garages, electrical shops and transmission shops, in addition to the Buerge dealership. Since Buerge put in the first replacement transmission at a cost of $2,300, it has not charged Gewant for the work. All of the transmissions were either new or factory rebuilt by Chrysler.

“I really can’t fault Buerge,” he said. “I believe they are trying to the best of their ability to fix the problem.”

Tony Walker, head of the Buerge service department, confirmed Gewant’s story and said the dealership has assigned its shop foreman to figure out the problem with the LeBaron transmission.

“It’s a tough one,” Walker said.

A Chrysler spokesman in Detroit said the company no longer equips its current models with the 604 transmission, and that whatever problem Gewant has with his 1990 LeBaron is not representative of today’s Chryslers.

Wiggins believes the transmission itself is not at fault in Gewant’s LeBaron. Rather, an electrical system problem may be forcing the transmission into a so-called fail-safe mode. Anytime the charging system voltage drops below 12.5 volts in the LeBaron, the car’s computer automatically puts the transmission into fail-safe, which allows the transmission to operate only in second and reverse gears.

Memmolo recommended that Gewant find a qualified transmission shop to fix his vehicle, beginning with a complete charging and starting system examination. He also said qualified transmission shops should have specialty diagnostic equipment.

The lesson of Gewant’s saga? When a shop or a dealer has trouble diagnosing a problem, it’s best not to spend years with a trial-and-error approach. Whether it’s air conditioning, cooling, transmission, engine or suspension, specialty shops often are better able to diagnose difficult problems.

Ralph Vartabedian responds in this column to automotive questions of general interest. Write to Your Wheels, Business Section, Los Angeles Times, 202 W. 1st St., Los Angeles, CA 90012. E-mail: ralphvartabedian@latimes.com.