I bought my 1998 Mustang new from the dealer and use it as my every day run around and drive to work car. At around 90,000 miles my rear-end started to make noise, it was a constant low pitched oscilating hum. Anyone who rode in the back seat would say something about the noise. I took it to a mechanic and he said the gears in the rear were MUSH. So I had the rear-end replaced. The mechanic found a rear end from a newer 4.6L mustang at a junk yard and changed it out for me. Is it a common problem in 1998 Mustangs? Is there any maintenece i should have been doing to prevent it? For 4 years I was driving the car 45 miles one way to work everyday on the Turnpike usually cruising about 75 MPH. Has anyone else expereinced this problem? The car now has 101,000 miles and has had NO other problems. Thanks,

Erik

 

There were no abnormal concerns in 98 on your diff. Sounds like you had a pinion bearing failure that caused excessive wear on the gears. the only possible thing you could have done is change the diff fluid every 30-40k.