1) 1985 Auburn. I thought the upper deck was going to collapse from all the stomping. Our fans nearly tore down the stadium. By far the loudest and craziest Neyland has ever been.
2) 1982 Alabummer. Again, could literally feel the stadium shaking.
3) 1998 Florida. This game has to be up there with all time loudest. Al Wilson singlehandedly dominated Florida and the crowd just got louder and louder and louder. The after game experience on the field and campus might be the greatest of all time.
4) Arkansas 1998. First half was flat as a pancake and quiet. The second half of that game is arguably the loudest. That fourth quarter was when I knew 1998 team was a team of destiny. Again, Neyland Stadium was rattling....
5) 2006 Cal was very loud, wild and crazy. The Vols completely dominated. The hype that whole week and pregame with all the **** talking by Cal people and team caused a huge ruckus that carried over through the game by fans and obviously the players. That was an exciting day in Neyland. Just a good ol fashioned ass kicking.....
Honorable mention: 1992 Florida game in the absolute rain downpour. It was raining so hard you could barely see the field. The Vols dominated Florida the entire game. Complete dominance!! Usually people leave their seats or run for shelter. Not that day, every body stayed put and didn't care because it was worth every bit of being completely soaked. No one cared. The place was rocking that day despite the weather. Mose Phillips was a hero born that day!!!!
Bama 82 during the Worlds Fair.
The single loudest moment I can remember is Travis Stephens taking the screen pass in against UGA in 2001. For about a minute it was absolute pandemonium in Neyland - couldn't hear yourself, the upper deck was shaking, all that. Sound wasn't quite as fancy back in 2001, but the video below conveys it well enough (just don't watch any further after the extra point).
Georgia vs. #6 Tennessee 2001 - YouTube
2004 Florida is the second loudest I can recall, especially the field goal itself. The cheering started at the other end (I was next to the band in the other endzone), and fell across the crowd in waves. One of the most amazing things I've ever seen in terms of a crowd reaction -- a ripple of Volunteer frenzy.