I own a 1991 Ford F250 7.3L Diesel with the 5 Speed Manual ZF S547.Question:  When I depress the clutch pedal I hear a high pitch squeal.  This truck has been trouble free what do you think it might be?Answer:  If this noise happens when the clutch pedal is pushed in and held it is generally caused by a failed pilot bearing or bushing to fix this problem order our "Input Pilot Bearing Repair Sleeve" (87-Up Except PTO) Parts Number MWTPBZ73HD $59.95 plus S&H.  You can see a complete list of parts we can supply for your ZF 5 Speed on our site.