Slipping into 4wd?

Whenever i accelerate hard from a complete stop i hear a popping noise from the front. Kind of like its trying to lock into 4wd. It only does it during hard acceleration. It makes the popping noise when its in 4wd also.... When i first noticed the problem i checked and the fluid was low. So i filled it back up and the problem still persist. What should i check first? 2004 4x4 with 55,000 miles.

Look to see if you have a broken motor mount, bad bushing on your torsion bar. Also look a the FQA's on How To's.
http://www.automotiveforums.com/vbulletin/showthread.php?t=496966
Thanks
SC

Yeah i have checked on the how to's section and none of them seemed to apply. I guess i will check the motor mounts and torsion bar bushings.

Yeah it was definatly the motor mounts! Took it to the shop and the drivers side was completley broken. Passenger side was cracked pretty bad.