thunking when in drive, with brake applied.

[dhe]

I noticed a very slight thunking noise, when my 2001-tracker, with 120K, is in drive, and I'm applying the break. Noise disappears when car is placed in neutral. Most people wouldn't notice, but I'm gifted or cursed, depending on how you want to look at it, with an ability to notice differences, in pitch, noise or vibrations.

I'm guessing it's some component that is suffering from age or wear? It's just something I noticed, and the automatic transmission shifts fine has no problem.

Thanks,
dhe