It's a hard one. If stock manual hubs there is nothing that can really go wrong unless it's stripped the locking collar that slides on and off the spline.. they usually smash out before that happens though..
I'm sorry to say but I'm thinking you'll be looking deeper.. it's really not to hard.
MudRunnerTD has done a brilliant build thread of it all with like 100 pictures so it's quite easy to follow..

A good time to check bearing grease and conditions.. and more importantly seals..