03 xterra noice when in gear

My Xterra makes a rattling noise when I put it in drive and reverse. It goes away when it is in neutral or park. Automatic transmission fluid level is good. Thanks for any help

I'd bet you have a bent heat shield that is rubbing on the exhaust somewhere. Have some one be in the car and have their foot on the brake while in gear, set the e brake, and chock the wheels. Then lay along the side (not under) of the X and see if you can hear the general area it is coming from. Then with the engine off, go back under and scout out the exhaust and it's shielding for rattles. Don't be afraid to bang you fist along the pipe and shields. You just might find it.

You are correct. Any problem with removing the lose shield?

The bolts that hold it on or together might need a shot or two of penetrating oil. I like PB Blaster myself. It will eat through the crud that has collected on the bolts from being on the undercarriage.