This what gear whine usually comes down too...a poor install. I really hope you get it fixed correctly. It shouldn't whine or howl.

 

What he said............ My 4.10 done at Ford, perfect from the first blast off.

 

Well I took it back. They replaced the Pinion bearing and the noise is still there. They have assured me everything is set up right and that every so often you just get a set that are noisy. Sooo.... I check with Ford and they said the same thing and that the only solution is to replace them. Jesus... This has cost me enough already. The mechanic at Ford said there is nothing "wrong" and I won't have any issues and that the whine may even fade over time a bit. So I took all this info back to the garage that diagnosed the pinion bearing and he said that this could very well be the case. Well screw it. I can live with it. It's not that bad and pretty sure it's not as bad as it was.

 

Guys, Ford changed how they fab the 4.10 gears last year. In order to make them stronger, they changed the facing on the gear teeth. Expect a little whine now.

If you've got too much whine at all speeds and motion, that's a problem, get someone to diagnose and make sure the whine is actually coming from the diff. Sounds like it's not terrible for you though. I'm expecting to get whine when I get gears this summer. Heck, I've got whine at speeds under 35mph on my stock 3.55s.

Things are never easy, are they?

 

Mine only whines on deceleration and only between 60-80KPH which is what made the pinion bearing the suspicion. In the end it cost me another $140 for new bearings and fluid but at least I know there is nothing wrong.

 

When mine were initially installed I know they got quieter within a week. Now after being reinstalled they are as noisy as the first time so hopefully the will quiet down again a bit. Also switched to Royal Purple from the Castrol I was using.