I have a 2000 mustang 3.8l and and the rear output shaft seel in the tranny keeps going out.. I have replaced it three times. Within the first 100 miles it'll go out again. What causes this? Its a 5 speed tranny.
Transmission output shaft bent or bushing worn, driveline slip yoke damaged ie nicked or egg shaped, driveline out of balance or bent. HTH
Can something be wrong with the rear end? That may cause a vibration that causes it to tear the seal out?
Anything is possible, but normally if there was a vibration in the rear end it would take out the pinion seal first, and you would hear something from the rear end.
I forgot to mention to check your transmission mount, if it is weak or broke that can also cause your problem.
Looking for a Used Mustang in your area?
CarGurus has 41,215 nationwide Mustang listings starting at $900.
Search Ford Mustang Questions
Ford Mustang Experts