I have had the car for 4,000 miles, and ever since I had the car on occasion when I first begin to reverse I get a single thump sound. It's been doin this ever since I had the car, and haven't taken it to the dealer, does anyone else ever have this problem, or know what it is? I'm just curious if its gona be expensive to fix, or wut. Any information would be appreciated.

It's most likely the ABS brake self-test. It is a pretty loud thump, that you can actually feel vibrate through the gas peddle a bit, but the only thing is that it doesn't do it just in reverse, unless you drive quite far in reverse. It usually just does it within the first 30 seconds of driving. A lot of people have been worried about this, but its normal, and described in your owners manual. If you search this forum, perhaps in the glossary, you'll find the existing thread and you can read all the detail, and find the reference to the page in your manual.

I have also noticed this too in my Rogue. I also noticed it in my 2006 Pathfinder. The pathfinder was pretty loud. Sounded like I hit something or ran over something. Haven't noticed it in the Alty though.

ABS self test. My Mazda does it as well only it is much louder. Nothing to worry about.