WHAT IS THE PITCH OR ANGLE FOR THE DRIVE SHAFT FOR A 1978 LINCOLN CONTINENTAL FOUR DOOR WITH 6.6 LITER ENGINE? WHEN YOU DRIVE HIGHWAY SPEED 60+ MPH I GET A VIBRATION IN THE SEAT AND FLOOR. I HAVE BEEN TAKING IT TO A LOCAL FORD DEALER AND IT EVERYBODY IS WONDERING HOW TO CORRECT THE PROBLEM.