I have 77K on my 1999 Super Duty. I bought the truck two years ago with just 23K on it. The truck sat for a while and was not used very much. I had the truck about a year and started hearing a howling coming from the rear diff. I took it into a shop and they (insert long story here) eventually replaced the carrier bearings which one was in very bad shape. I also had them replace the pinion and axle bearings. The ring and pinion were in good shape and did not need to be replaced. After picking the truck up there was still a little noise not very loud coming from the diff when at that point where your not under a load around 50mph. The shop said you may get a little noise because the ring and pinion may be running in a little differnet location? Plus being that I have a camper shell on it makes the noise seem louder than normal. I just let it go and have been living with it for about year but now it's really starting to anoy me. Is this a problem that is caused from setup of the ring and pinion and can it be corrected If I take it to a NEW shop?

Any Thoughts? Thanks

 

its probably the ring and pinion if they really replaced all the bearings that u say they replaced, if the preload and backlash are out of spec it will make noise, it can be corrected by adding shims to get the perfect gear mesh.
My question is instead of dumping all this money into this rear for parts and labor why dont you go to the junkyard and get a whole new rear axle, if its a 99 superduity the truck has a 10.25 full floater rear axle. they go for about 75 bucks at pretty much any junkyard and will bolt right in. make sure to get the same gear ration so u can use the 4 wheel drive withour grenading ur transfer case
- and im sure u kno but look for the (L) in the middle of the gear ratio for a limited slip, for example 3L55