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Discussion Starter · #1 ·
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.
 

· Supr Moderator AutoTech SS-Guru Mbr Extraordinaire
2015 High Country Duramax
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You need to stay 4.10 since your 4wd. Unless you want to swap the front too.

But, the cover is just some bolts and it's off. That will basically tell you all you need to know unless it's an axle bearing or the like. Could be the spider gears, since during turns is when they spin (any time the wheels are moving different speeds, they move).

To fill the fluid back up, you'll need around 3 quarts of 80w90 or 75w90 gear oil. Fill it until it's just below the fill hole.
 

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Discussion Starter · #3 ·
You need to stay 4.10 since your 4wd. Unless you want to swap the front too.

But, the cover is just some bolts and it's off. That will basically tell you all you need to know unless it's an axle bearing or the like. Could be the spider gears, since during turns is when they spin (any time the wheels are moving different speeds, they move).

To fill the fluid back up, you'll need around 3 quarts of 80w90 or 75w90 gear oil. Fill it until it's just below the fill hole.
So the front diffs are different based on the rear gear ratio? I always thought it was either the 8.25 front or the 9.25 front for the HD. Either way, thanks for good info.
 

· Supr Moderator AutoTech SS-Guru Mbr Extraordinaire
2015 High Country Duramax
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The 1500s are 8.25 and the HD trucks are the 9.25. The gear ratio is what varies from truck to truck. And both the front and rear ratios need to match otherwise it'll be trying to spin the front and rear diffs at different speeds and something will break ( either the transfer case, differentials, u joints, etc)
 

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You need to stay 4.10 since your 4wd. Unless you want to swap the front too.

But, the cover is just some bolts and it's off. That will basically tell you all you need to know unless it's an axle bearing or the like. Could be the spider gears, since during turns is when they spin (any time the wheels are moving different speeds, they move).

To fill the fluid back up, you'll need around 3 quarts of 80w90 or 75w90 gear oil. Fill it until it's just below the fill hole.
Yep, you will readily be able to tell. If it is just the spider gears, you can probably do this job yourself. If it is the ring and pinion, I suggest you let a pro do that as you need to do some careful space checking to make sure your ring and pinion aren't destroyed the first time you drive it.

I replaced the spider gears in my son's Ford Ranger years ago. Not hard at all.
 

· SilveradoSierra Guru
2004 Sierra 3500 6.0L, auto, extended cab, cab&chassis, upgraded to 4wd
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Look at the RPO code sticker in your glovebox, to see if your rear dif has a G80 (a type of locking rear diff). If the sticker with a bunch of 3 letter/digit codes, includes a "G80" entry, then you do.
 

· Servicemen
2021 GMC Sierra Denali CC 4WD Ultimate 6.2L
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8.25 and 9.25 are the ring gear diameter.
 
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