I was rolling about 2 mph while dialing out of 4 Lo while driving on pavement. And there was the nastiest "Bang" gear noise from the front end. It damm near shook the whole truck. Then the 4LO light wouldn't go out intell the wife backed it up for like 100ft a few times.
So far everything seems fine, but I wonder what real damage was done. I asked another 06' Dodge auto tranny owner if he ever had this happen and he said he had something similar.
Just how common is this??

 

Must have just "unloaded" the front half of the drivetrain. There are no coupling devices forward of the t-case.

Backing up has no bearing on unlocking anything on a 3rd Gen truck.

Why shift out of low while moving?

Don't stress on it.

 

Don't worry about it - probably had the drivetrain loaded, due to gravity or your right foot.

Best way to shift is barely moving, no throttle and firmly push lever.

They do make a pretty good bang if you pop 'em the wrong way!

 

^ Push lever! Or turn ****.

 

Next Differential fluid change inspect your ring gear closely.