Theres usually a little bit of backlash in the gears but shouldnt be much. Does this pop in 2wheel drive or only 4? or in both? Have the gears been switched out? Is there a locker?
If the gears have been switched out, there is a chance that they could have been installed incorrectly. If the pattern is a little off it can cause big problems.
If you can, remove the front diff cover and see if there is any damage to the Ring gear. With the diff cover off is a good time to turn your front drive shaft to see how much backlash there really is. Make sure to have the front on jack stands when doing this.