I have a 2006 Silverado 1500 z71 4x4 w/ vortecmax 6.0/4L70 and 4.10 rear. Also has the electronic suspension if it matters. The rear end makes a grinding noise very noticeable around speeds under 30mph, the tone is consistent with the speed. The shop I brought it to said the rear pinion gear was probably the culprit but they couldn't hear it as easily as I can and advised no work was currently needed. Taking apart the rear differential isn't something I'm comfortable or knowledgeable about, but I'd personally be willing to just swap the entire rear axle out. If I can get ahold of a good rear axle from a local part out, does it need to be a 4.10 rear? I'd prefer a 3.55 or 3.73, whichever the typical 1500 silverados come with to help lower highway rpms and maybe increase mileage. I don't tow enough to justify needing 4.10s. Can I swap in a lower ratio rear end without changing anything else, will the front differential be fine? Lastly, is it worth swapping the entire rear axle myself vs having a shop go through the rear end and fix it themselves? Thanks much.