Simon1

I will only have someone who guarantees their work do the rear end on my car. I found a guy here locally that does this, he has done two installs, both silent. FRPP gears. I also have had motive and Yukon. Both were quiet, installed by a pro.

Parts are important, but expertise is more important.

It is truly a part of the car that can kill a driving experience.

tx_zstang

If the gears were new, bearings all new and installed properly, there should be no howl from the rear end whatsoever. However, in the 373's gears in my blue Mustang, I intentionally left the backlash a little on the looser side (0.015"), and I get some noise right at 40 mph and then a little more at one other higher speed, but quiet at all other speed. I attribute this to the looseness of the backlash, as all other gear installs I have done, from 355's to 410's, have come out far quieter when everything is installed very close to dead-middle in regards to specs.

Did you put red loctite on the pinion nut? And/or did you use a new pinion nut? They can work loose, which would be bad!

After the differential was installed, did you check ring gear run-out? It is easy to skip checking it, but is something I check now. Or at the very least, did you check backlash at more than one location on the ring? What can happen is if the ring gear is not perfect or if there is a spec of debris in the way when installing the ring to the carrier, it can make the ring run at a slight angle, and that will cause noise.

Something else to consider: were the axle bearings replaced? Sometimes they can get a little noisy. On a full rebuild, I like to replace them as well.

Generally though, if all the procedures and measurements were followed, and FRPP gears were used, if the noise is just at certain times and is not bad, you can leave them alone.