Brake light switch or throttle position sensor are the two most likely suspects that I mentioned previously. The problem is we hate just throwing random parts at a problem without doing any diagnosis first. That is the most expensive and least effective way to solve a problem, however, the most effective way involves connecting a scanner to the car, then taking it on a test drive. Most people don't have access to a scanner so we have to resort to just trying new parts.
One simple thing you can try is holding the brake pedal up with your foot when the problem occurs. If that makes the problem stop, try readjusting the brake light switch. If the problem occurs more often at one specific speed or when you move the gas pedal just a little, suspect the throttle position sensor.
Some shops have a scanner that they can connect to your car that has a record / playback feature. You press the record button as soon as the problem occurs. Because the data travels through the scanner's memory, the recording actually begins a few seconds before you pressed the button. Later, the data can be replayed while watching for what caused the torque converter to unlock.
Of course, this all assumes that's what's happening. There really shouldn't be any noise associated with the converter unlocking unless the converter is what's causing the problem. A transmission specialist might be able to tell that on a test drive.
Another way to find the source of a noise is by using a tool called a "Chassis Ear". That is a set of six microphones, a receiver, and a set of head phones. Many mechanics have never heard of or seen this tool. You clip the microphones to suspect points under the car, then switch between them while listening with the head phones on a test drive. Moving the microphones around lets you zero in on the source of the noise. The tool costs $200.00 from Mac Tools. I can post a link to their web page that shows what it looks like if you need it. It's available from the other tool truck guys too like Matco, Cornwell, and Snapon.
Saturday, February 5th, 2011 AT 10:26 PM