Maybe you did, but i would think probably not. Now when you say rattle is it in neutral? Say coasting down the highway at 50 or 60? Mine sounds real nasty in neutral, Kinda like a nasty rattle. I assume its just from the 4.7's running extra noisy and maybe even a little more with no torque on them.
You may be able to access the chain via the drain or fill hole and check it out. Also you could pull the front driveshaft off the tcase, put it in 4 and see how much play you get on the front output shaft.
Fromt what i have heard and from others with crawl boxes every one will sound different, and they never sound happy.... Some are just more not happy than others. Its common for them to have a gritty sound.
Let me know what happens with this, if it ends up fried at least these tcases are cheap and semi available