Door problem

00 tahoe obs. when the front drivers door is closed and i hit a bump the door makes a rattle noise like its not closed. Any ideas what needs to be replaced. when the door is closed looks to be flush with the rest of the truck.

Most likely the door latch in the door itself. It's obviously latching, but I'd bet it's shot. It's not too bad to replace. You'll have to take the inner door panel out to remove it.

Is it easy to close shut or do you need to "slam " it? Mine does that but does not rattle. The "stud" on the jam looks ok so I'm wondering if the mechanism inside the door is worn. It is only the driver's side door.

are you sure the latch is catching fully closed. If the latch is in the first catch it will rattle. If it is only closing to the first catch of the latch you need to adjust the striker out.
You did not state if you see the door moving or only here a rattle noise. Seeing the door move is a dead giveaway to a latch/striker issue. I use my hand or thumb across the inside rear door gap to feel for movement between door and cab when driving over a bumpy road. You can feel abnormal movement easier than you can see it. Ext cabs with rear doors are flimsy and move alot, but this should work on your Tahoe since it has a B pilar.
I can tell by the sound of the rattle, but I cannot hear your truck.
Often the rattle is from internal linkage rods in the door. They make a different sounding rattle than the latch issue will.
With the linkage rod rattles you will not see the door move.
Holding some pressure in both directions on the lock knob and door handle while listening for a change or elimination of the sound can tell you it's a linkage rod problem before you remove the trim panel.
I have worked on a ton of farm trucks (notorious for not shutting the door all the way while driving across fields) and have replaced very few latches. I am not saying you don't have a bad latch, but do some diagnostics first.
A hard to close door or door that drops when opened is a sign of worn hinges which could over time damage a latch. Usually you are going to get irritated and fix the problem before it's bad enough to ruin the latch.
A latch could also be damaged by lack of lube or if it had NVH plastic on it that peeled and caused it to bind and the door was slammed shut with the latch rotated wrong because of the bind. I do not recall if the 00Thaoe had NVH plastic on the latch.

Also check the hinges. If they are wore out, the door can and will bounce around once its closed as you hit bumps in the road. To check, open the door, and lift the latch side to see if the door is loose on the hinge pins. If so, you will need to change the brass bushings.

Just went through this with mine. If the plastic is smashed out of your latch mechanism, your door will rattle on the striker bolt. Here's a pic of my new latch and you can see the clear plastic in there. No more rattle

95 rcsb, L33 5.3, hot cam, frost tune, 5spd, 4/6