My guess would be that you have stretched the chain. The "bang" you are hearing is the chain jumping its sprockets. Been there done that....best bet is to try to get a replacement tcase (~ AUD $600 fitted from a wrecker) from a very early model that actually have a chain about an 1/4" wider than the later cases (pulled down both for inspection).

www.kiatechinfo.com is your friend if you want to pull it out and look. (straightforward)

We need to get onto Fokion's mate to get stronger diffs that will let us wheel with ease. (More importantly reduce the shockload from lifting wheels that causes damage such as this).

Hereby proposing a group buy of the front locking diffs. Any real takers????????