before the last 2 days, this only happened twice in like 3 months but now it has happened 3 times in 2 days. Anyways when I start my car and go thro first and switch into second at like 3-3500 rpms, there is a "clunk" noise coming from the under the hood and then it doesn't do it again until I start my car again after a few hours. Does anybody know what this is?