My 4 wheel drive works, but makes an awful grinding sound. Even just driving around in 2 I hear a rattling coming from it. Sounds maybe like the chain came off or something? Is there anyway to know for sure what's wrong without taking it apart? And do you think from the sound of this I will need a new one? Anything you got helps, thanks a lot

 

Your chain didn't "come off" could have a few broken links dragging against the case. You could drain the fluid and look for metal or just face it and open it up

 

Sure it's actually the case? How do you know?

 

I throw it in neutral and go under the drive shafts, front one doesn't budge but the rear one rotates a little and makes a ratcheting sound from the tcase.
I'm positive that my tcase is the problem.

 

Those chains sometime stretch over time and start skipping but if you can make it skip by turning the driveshaft by hand, something else may be wrong. Possibly not positively engaged or extremely wore out chain.
Not very hard to rebuild but sometimes you can find a good used one for cheaper than the chain alone. Last time I bought one it cost a little over $100 bucks

 

Have you tried shifting the thing manually to make sure your linkage isn't the problem? A slight "ratchet" is normal as long as its not like REALLY ratcheting.

Just as an FYI I just bought an Np242 TCase with a rubicon express HNT on it with an xj front driveshaft for $100. You might be better off looking for another case on Craigslist or a local offroading club.