Hello, the snapping noise is usually a sign, that a front axle universal joint is worn. These will need to be inspected and replaced.
As far as the 4wd drive not engaging, you may have linkage to the transfercase binding, a broken joint at the axle or propeller shaft or internal transfer case damage. The fluid should be changed every 30,000 mi. By the way, I have also seen in some cases that mismatched tires, and tread depth cause 4wd engagement and disengagement problems.
Before beginning repair on a suspected transfer case malfunction, check all other driveline components beforehand.
The actual cause of a problem may be related to such items as: front hubs, axles, propeller shafts, wheels and tires, transmission, or clutch instead. If all other driveline components are in good condition and operating properly, refer to the Diagnosis Chart for further information.
I hope this helped if so an accept is appreciated
In 2001 Dodge used and actuator to engage the front axle. This is mounted to the right rear of the front axle. If you have vacuum to the front when applied, the collar may be stripped inside the front axle housing.
The disconnect axle control system consists of:
The shift motor receives a vacuum signal from the switch mounted on the transfer case when the vehicle operator wants to switch from two wheel drive mode to four wheel drive mode, or vice versa. When this signal is received, the shift motor begins to move the shift fork and collar within the axle housing. In the four wheel drive mode, the shift collar connects the axle intermediate shaft to the axle shaft to supply engine power to both front wheels. In two wheel drive mode, the shift collar is disengaged from the intermediate shaft and the intermediate shaft is allowed to free-spin. When the two shafts are disengaged, the load on the engine is reduced, thereby providing better fuel economy and road handling.