There were a few items that needed attention before my next road trip. Last year I installed new U-joints, replaced the rear axle bearings, and replaced the troublesome carburetor. I replaced a bad front wheel bearing yesterday, and I have to order new door weatherstripping to stop the wind noise that nearly drove me mad on my trip to Buick Gardens last Fall. A new issue came up since then that so far has eluded me.
When the car is cold I can hear a low thumping noise coming from what sounds like the front of the car. It disappears when I apply the brakes. After the car is driven for a short while, say around 20 minutes, the sound gradually fades away. I can feel no vibration or other tactile sensation in the chassis, steering wheel, or brake pedal. I'm not sure where to look since everything looks good under the car and inside the brake drums. My first thought was a tire because the noise dissipates after I drive for awhile and the tires warm up a bit, but applying the brakes wouldn't affect tire noise, at least I don't think so. Suggestions?