Is a transmission flush worth the money?

Trouble with your transmission?

If so, you may be reaching deep into your pockets. Replacing or rebuilding a transmission can cost several thousand dollars.

Although there's not much maintenance to keep your transmission operating properly, one preventive maintenance measure some mechanics stand by is a transmission flush. Flushing a transmission is the process of mechanically removing - or flushing out through the use of pressure and a cleaning agent - all the old fluid, built-up debris, and contaminants and putting in new fluid.

Some mechanics say a flush can prolong the life of the transmission. If the transmission is slipping, making a grinding noise, or there's a lag in acceleration after applying the gas, it could be an indication that the vehicle is low on transmission fluid or could be in need of a flush.

"The way I describe a flush to my customers is that it's kind of like a dialysis machine for your vehicle," said Daryl Nelson, owner of J & R Auto Repair in Glen Ellyn, Ill. "It pushes all the old, dirty, and contaminated fluid out and, while that's happening, it's refilling it with nice, fresh fluid."

Mechanics who recommend flushes say the service should typically occur every 60,000 to 100,000 miles.

However, some mechanics recommend avoiding flushes for a number of reasons.

David Waits, owner of Japanese Automotive Service in Hilliard, Ohio, performs flushes only if antifreeze has contaminated the transmission fluid. He recommended a transmission drain once a year, which is the process of manually draining much of the old fluid and replacing it with new fluid. No special machine or cleaning solution is used during a drain.

"I personally believe most flush sales are to generate money for the company selling the flush, are not beneficial to the vehicle, and don't follow the manufacturer's recommended maintenance," he said.

Sean Avner, owner of A Team Transmission in Columbus, Ohio, said it was important to consult a trained transmission technician before having any service done.

"We've received numerous phone calls to tow vehicles out of shops that have been flushed," said Avner, who adds that he has seen cases where flushes have damaged internal seals on a transmission. "If that isn't the cause, we've found that a lot of shops have not been trained sufficiently to operate the machine, and have damaged transmissions as a result. The best bet is to take the car to a transmission specialist. They can determine if the transmission is serviceable."

Mechanics recommend checking your owner's manual to see what the guidelines are for flushes and drains. Some newer vehicles come with transmission fluid designed to last the lifetime of the vehicle.

Jeff Gunning, service manager with Addison Auto Repair & Body Shop in Denver, said flushes helped keep the transmission running in optimal condition.

"The biggest benefit is the newer, cleaner fluid helps keep the transmission running at the temperature it needs to be, and newer fluid has better lubrication properties," Gunning said.

According to the experts we spoke with, expect to pay $200 to $250, on average, for a flush.