I have a 2000 Chevy suburban it starts up fine but when you put it in drive or reverse it won't move. What could be the problem

 

Well... any error codes? or Check Engine Light?

I'd start with a possible transmission issue. When was the fluid last replaced? What's the current level?
Could also be the shift cable. I believe in 2000 there was still a metal cable connecting the shift lever to the trans. (vs. electronic). Does the truck roll when in D or R? If it feels like it's still stuck in park, maybe it's not actually shifting?

 

The levels are full and when I put it in drive or reverse it doesn't roll move nothing

 

My 2002 Tahoe had the clip that holds the shift cable on the linkage on the transmission fall/rot off. The lever moved at the steering column but never moved the linkage on the side of the transmission. If I remember correctly, when this happened, the **** indicator did not move when the lever was moved.

 

That's my thought. something cable wise isnt' getting from the shift lever to the actual tranny. Which just means you're still in Park.

 

It's just like the Bowden cable on a lawn mower throttle. If the cable housing isn't constrained then it will just move with the cable itself and not do any actuated.