Offroad Trailblazers and Envoys

Rear Diff Recommendations

G80, GU6, GT4, GT5, WTF? This section is for gearing and driveline stuff.

by MrShelley » Fri Jan 06, 2023 12:55 pm

Posted this in the Offroad section of the sister site as well...

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).

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

Posts: 18
Joined: Mon Feb 15, 2016 12:08 am
Name: Todd
Vehicle Year: 2008
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD

by xXxSilveradoxXx » Mon May 22, 2023 9:48 pm

I've got a TruTrac in the Trailblazer. I really like it, but I also don't do gnarly things with the rig. Took it to Usal Beach in January and it didn't miss a beat.

The old G80 and 4.10s.

New Trutrac and 4.56s.

Stock 10-bolt 8.6 versus the 14-bolt 9.5.

All buttoned up.

Usal Beach
2004 EXT, V8, 14-Bolt SF w/Trutrac, 33s, Long Tubes with true dual exhaust.
Posts: 12
Joined: Thu Jan 28, 2021 9:38 pm
Name: Pete
Vehicle Year: 2004
Vehicle: Chevrolet Trailblazer EXT
DriveTrain: 4WD w/ Limited Slip

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