This is on my '05 TB EXT LS 4WD with 256,000 miles. Sometimes, when I hit a bump while driving, be it a bump in the road, railroad tracks, etc., there is a horrendous rumble/vibration that sounds like my whole front end is going to fall apart. Sometimes it lasts for half a second, and sometimes it lasts for a few seconds (the worst I had was about 4-5 seconds). It will than go away and drive smooth like it never happened. I just replaced sway bar link thinking it was that. It is actually very occasional. It only happens every few days (its a daily driver). The only thing I can think of even close to that, is when I was replacing the wheel bearings last week, I noticed a lot of play (0.5-1" in all directions) where the passenger CV axle goes into the axle disconnect assembly. I wonder if when I hit a bump, it lets that CV shaft up a little and it centrifuges the tripot on the shaft around causing the rumble/vibration. It seems to happen more often at higher speeds but I have had it happen when going 20 mph over railroad tracks but it seemed to match the vehicle speed relatively. The only other thing I would think of is a motor mount. anyone have any insight?