The random vibrating coming from the front end sounds like the death wobble to me. Also when that transfer case fails it defaults to locking all four wheels together and it shouldn’t make a deafening grinding noise when it fails unless you broke the chain inside. If you think it’s your transfer case I would check the fluid level. Also does it jump and buck when turning corners?
1995 Jeep Grand Cherokee Limited 4.0L NP249 Transfer Case, 42RE, 199,000 miles
2002 F150 Lightning 385 hp
1969 Mustang Mach 1 428cj 4-speed 3:89 gears