On some 2006 model year Nissan Titan and Armada four-wheel drive equipped vehicles, there is the possibility that the bolts attaching the front drive shafts to the front final drive assembly may not have been tightened properly. This may result in the front drive shafts coming loose and cause a vibration or noise in the vehicle front end. If the front drive shaft becomes disconnected, it may be damaged or cause damage to other vehicle components. However, the ability to control the vehicle will not be affected.

Read the compleate bulletin here:

http://www.nissanhelp.com/Ownership/Bulletins/Nissan/2006/NTB06-012.htm