I downloaded a 2003 file for hp tuners to see what it said and ys... its just some wierd ratios in the speedo section for you.
You may be in luck though because according to tiresize.com a 285/70r17 which is about 32.5" and 4.10 gears make the output shaft spin at the identical speed as the stock size tires with 3.73 gears.
just run them
Statistics: Posted by jerflash — Mon Sep 30, 2024 9:08 pm
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So take a look to the attachement, anybody have an experience with those parts and could tell me if they're ok or not ?
Thanks community !!!!
Statistics: Posted by jeantalus — Tue Aug 01, 2023 4:01 am
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Statistics: Posted by flyboy2610 — Sat Jul 29, 2023 11:42 am
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Thanks community
Statistics: Posted by jeantalus — Thu Jul 27, 2023 9:41 am
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The old G80 and 4.10s.
20210319_153900.jpg
New Trutrac and 4.56s.
20210918_171659.jpg
Stock 10-bolt 8.6 versus the 14-bolt 9.5.
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All buttoned up.
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Usal Beach
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Statistics: Posted by xXxSilveradoxXx — Mon May 22, 2023 9:48 pm
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In preparation for swapping the factory 8" open rear out of the Trailblazer I've procured a G80 equipped 3.42 geared rear from a Trailblazer EXT. I've also bought 4.56 gears for the front and rear (practically stole them after Christmas gift cards). Before I install the 8.6 rear in the truck I'm going to freshen everything up (seals, bearings, etc) while also having the new gears installed.
That's where my question lies. What is the recommended diff for the 8.6? Any other options I should consider?
Factory G80
Yukon DuraGrip YDGGM8.5-3-30-1
Eaton TrueTrac 913A481
Yukon Grizzly Locker YGLGM8.5-3-30
The vast majority of the miles on the truck are in town, but I'm anxious to explore more of the BLM land and National Forests in New Mexico. Lots of rocky, steep terrain. There are also some trails around here (East Texas) where I could definitely use more traction. I like the idea of the locker, but concerned about streetability as well as noise (the wife drives the truck sometimes).
CURRENT SETUP
2008 Trailblazer LT 4WD
MarkMCs 3" body lift
MarkMCs 3" suspension lift
MarkMCs 1.5" wheel adapters
Helo 835 wheels (17x8)
Massive Speed Systems Adjustable Panhard Bar
Bilstein 24-103336 Front Shocks
Bilstein BE5-6248-H5 5100 Series Rear Shocks
Flipped Front A-Arms
BF Goodrich All-Terrain TA KO2s (285/70/17)
MDB Fabrication Front Bumper (HardTrailz old bumper)
MDB Fabrication Armor/Skidplates
Hayden Trans Cooler (Model 678)
KC HiLites LZR Lighting (replaced Kawells)
Pending: 4.56 Gearing (ready to install)
Custom Roof Rack
Fold-Down Fullsize Spare Carrier
Winch
Statistics: Posted by MrShelley — Fri Jan 06, 2023 12:55 pm
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If I remember correctly, first, I didn't research the ABS switchover at all and got an earlier rear end because I found a really cheap one (compared to any 2006+ I could source at the time). So when the shop installed the 4.56 gears into the axles they brought up the issue of the rear not having the connections for the ABS leads
The solution at the time was a piece of black tape over the ABS light 
I'm pretty sure I did the whole like that ... no ABS. It was about a year later that I found a 2006+ axle for a decent price and got it swapped again.
And with the tuned OS, I had no idea of the pre-2006 restrictions. PCMofNC just said they can program any gear ratio and when I told them I was going to change gears later, they suggested HPT so I could do it myself.
So what you are saying (for my clarification) is that for a pre 2006, PCMofNC could not do a tune that included a 4.56 gear ratio? If that's the case then I really lucked out back then when I ended up finding the very low km, GM exec-only driven 2006 LTZ on a Chevy lot in Listowel, Ontario. A tiny farm community about 1:45 from where I lived at the time. I checked on Google, that dealership is still there ... good for them!
Statistics: Posted by AlekG — Tue Mar 30, 2021 1:17 pm
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