1996 Other Nissan Models Need Help Bad

So, I have a 96' Nissan 200 SX SE-R. It has 162,000 and has been maintained pretty well. Runs smooth and no major problems besides the usual tune-ups and wear and tear problems. Just the past day I was driving when all of the sudden, it sounded as if my front right tire whet flat on the interstate, so I pulled over to check it out and nothing seemed out of place. I got back in and proceeded to drive for another 2 miles when all of the sudden I heard a "grinding noise" it sounded like I was driving on my rim and the trie was completely flat, but once again I got out and checked the tire pressure was ok. I could feel the vibrations and grinding noise coming from right below my driver's seat. The car would not go more than 5 mph without making the loudest grinding noise I've ever heard. I checked my transmission fluid to see if it was low and thought mabye the gears were grinding, but the level was fine. I have no idea what to do and need some expert advise. Thanks