When I put my Sportage in 4wd and take off it sounds like something is binding up. I'll get a loud banging noise every few seconds and when I hit the gas. I've checked and regreased both front hubs, checked and greased the front drive shaft. What else should I check?

2001 Sportage, TJ 106's, Everet spacers and bumpstops, Bilstein shocks on the rear, cone filter, Crager wheels, 235-75-15 Goodyear tires. Custom front winch bumper by Dave Scott. Currently DOA, but it is a work in progress.
2011 Kia Forte EX