What Causes the Transmission to Make Abnormal Noises When Braking in an Automatic Car?

[BradleyFitz]

Automatic transmission making abnormal noises when braking may be caused by clogged valves and pipelines inside the transmission, which disrupt the sequential regulation and control of oil pressure. Here is more information about automatic transmissions: 1. Under normal circumstances, the automatic transmission fluid should be replaced every two years or every 40,000 kilometers. 2. The automatic transmission requires regular inspection and timely replacement of the transmission fluid as per the manufacturer's requirements, using the specified grade of transmission fluid. 3. Only about 30% of the total transmission fluid is drained through the drain bolt, and in such cases, the use of transmission cleaners is not recommended.

[McAxel]

I've been driving for almost ten years and have encountered similar issues. When stepping on the brakes, the transmission makes abnormal noises, mostly due to aging transmission oil causing insufficient lubrication, resulting in gear friction sounds. It could also be wear and tear on the linkage components between the braking system and the transmission, such as a stuck valve body or sensor. Last time my car had this issue, the noise sounded like metal grinding. After checking, it turned out the oil was too thick, and changing it immediately fixed the problem. Don’t forget to check the oil level during regular maintenance—if the color is dark or black, it’s time for a replacement. Ignoring it could damage the transmission, leading to costly repairs. Nowadays, I perform simple checks myself every year to avoid trouble. Safety comes first—if the noise persists, take it to a professional shop for diagnosis right away.

[Viola]

I'm a new driver who just bought a car half a year ago. Recently, there's always a squeaking sound when I brake, which transmits to the transmission area. I asked an experienced friend, and he said that braking in an automatic car triggers the transmission lock. If it's loose or lacks lubrication, it's prone to abnormal noises. Other reasons include rust on the brake discs or small stones stuck, causing noise transmission. He suggested gently pressing the brakes a few times to see if the temporary issue disappears. If not, don't delay to avoid worsening the situation. Like last week, I went to the 4S store, and it didn't cost much to fix. Remember driving safety—if the noise gets louder, pull over. Timely handling can save trouble and money.