Mine has a little jerk like that in 4 low. All my trucks i have ever owned do that in 4 low. Maybe you are talking more of a violent action then normal or something?

 

This is my first 4wd truck. Never drove one with auto hubs. The truck sat for a year. This week I'm changing the diff. Oil and see if that makes a difference.

 

Get rid of the auto hubs! The auto Hubs are terrible and wear out very quick! And in high torque situations they almost never hold!

 

Here is a better explanation of the jerking.

When it starts roll, as everything is locking in I assume, jerks hard enough to kick the tires loose and there is a thud sound. Every time on acceleration.

Doesn't happen in 4 high. If this is something normal then its no worries. I just want to make sure if I ever use it, its not going to break something.

 

Probably not hurting so long as fluid levels are normal