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4x4 gear change

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Old 05-17-2011, 07:27 PM   #1
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Default 4x4 gear change

SO Ive been reading some threads on changing gears but havnt seen much on doing it on a 4x4 and was woundering how hard it is to do? Iam mechanically inclinded but have never done a gear swap. I have an 09 4x4 5.3 crewcab 6 speed and right now has 3:42 gears. I have read that guys are going with 3:90's and getting better fuel millage and that is what Im after.
Thanks in advance

2009 Sierra crewcab 4x4, 5.3 6 speed, catback exhaust, 4:10 gears
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Old 05-17-2011, 07:37 PM   #2
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I cant comment on the 3:90's but I can concrete tell you 4:10's will run awesome and get great mileage. If you have a dial indicator a drag meter and basic other tools it is cake to do. This is coming from a mechanic so my cake could be someone else's nightmare.

It really isnt too hard the one thing that will make your life way easier is to get the gear change kits that are complete. And make sure you grab an assortment of pinion and carrier spacer shims so you can get it dead nuts on. Be prepared to spend some time on it and you will be rewarded with a dead quiet rear end and OE life expectancy.
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Old 05-17-2011, 08:03 PM   #3
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Pretty sure 3.90's are not availalble for the front transfer case ........go 4.11's ......... changing the rear is pretty basic if you have paitence and measure 3 times but the front transfer case is not that easy ........
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Old 05-17-2011, 09:06 PM   #4
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the front diff you will actualy need to pull the complete diff off the truck , just un-bolt the two axles and all this other cracp them with some elbow grease it should come out make sure you have at least 1 buddy helping you out , the diff is perty heavy ..........
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Old 05-18-2011, 11:24 AM   #5
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After moving a complete rear axle with leafs, shocks, and brakes (minus wheels), my 9.25" IFS that's sitting in the garage doesn't seem too bad, lol.

That being said, you WILL wan't a buddy when working that biatch out of the truck... It'll be a PITA, lol

The reason you don't see as many gear swaps on 4x4s is because not many want to deal with that front diff removal.
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Old 05-18-2011, 11:36 AM   #6
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The front diff on 2007-up NNBS is easier to get out then older models. You probably could do it with a jack by yourself.

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Old 05-18-2011, 04:44 PM   #7
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Thanks for the responces guys. Im just wondering how hard the gear change is in the front diff (once it is out) to do. Once it is out of the truck is it similar to doing the gear swap in the rear end? I know a guy that I believe knows how to do a gear swap in the rear end but I dont think he has ever done a front diff.
2009 Sierra crewcab 4x4, 5.3 6 speed, catback exhaust, 4:10 gears
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Old 08-31-2011, 07:25 PM   #8
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Default gears

just fyi no 3.90's available for the 4x4. i run 33's and im goin 4.11. Just for eference when you go to change best price anywhere is from rons machine service look him up ull love the price. And trash that g80 timebomb while your in there ang get a true trac or comperable.
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Old 09-01-2011, 10:39 PM   #9
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I went with 4.10s when I did mine and it was like night and day, what a difference. I say do it, epecially if you have the lowly 3.42s like I did.
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