For those that have replaced the rear upper or lower trailing arms and may have a slight driveline vibration at 80k's and over especially if the car has been lowered try this... Back car up onto ramps, apply handbrake and chock front wheels front and back. Get under rear of car and loosen all trailing arm bolts. Start car and idle in reverse (ENSURE HANDBRAKE IS ENGAGED AND WORKING) if unsure have someone apply the brake. While car is in reverse gear and idling re-tighten all trailing arm bolts. What this will do is ensure the diff is tilted forward to give more positive pinion angle and may even in some cases stop the driveshaft from hitting the floor.