It is not the chain because the chain is not used when in 2wd, only in 4 hi/low. On some of these transfer cases there is a snap ring on the output shaft in transfer case that holds it in place and if it breaks the output shaft will slide out of the drum in the transfer case which will cause the truck to feel like the transmission is no good. If that is not the problem then a shaft in transfer case broke. If it is the snap ring, put it in 4 wheel hi and the truck should move, if it doesn't check to make sure the front differential lock is working if it is equipped.
