Rear Diff Recommendations

MrShelley

Registered Member
Original poster
Feb 14, 2016
11
Kilgore, Tx
In preparation for swapping the factory 8" open rear out of the Trailblazer I've procured a G80 equipped 8.6" rear out of 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
KC HiLites LZR Lighting

Pending: 4.56 Gearing (ready to install)
Custom Roof Rack
Fold-Down Fullsize Spare Carrier
Winch

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Ilikemy3s

Active Member
Dec 3, 2011
324
Dang nice looking truck. How many miles you have on that? I have no experience on what your are planning, so I can comment, Only think I have is that I thought our truck only went up to 4.10 gears. I might be wrong. Good luck with the build. Got any more pics ?
 

Mooseman

Moderator
Dec 4, 2011
23,693
Ottawa, ON
I'm also curious as to where you found gears for the front diff. These trucks only came with 3.42, 3.73 and 4.10 gears. At least being an '08 you can have the speedo adjusted via a tune.

From what I know, some serious wheelers call the G80 the gov-bomb and when it does blow, they're stuck getting out with just the front diff working. I've also seen my son's Silvy G80 blow up just from one wheel on ice and the other on solid asphalt on the road. Another one I've seen where a Suburban was just doing a one wheel peel in snow with it's G80 refusing to engage. When it works, it works, but when it doesn't...

I can't advise on any of the aftermarket lockers. Have you tried our sister site ORTB? There may be more info there regarding off-road stuff.

Good looking rig BTW :thumbsup:
 
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MrShelley

Registered Member
Original poster
Feb 14, 2016
11
Kilgore, Tx
I'm also curious as to where you found gears for the front diff. These trucks only came with 3.42, 3.73 and 4.10 gears. At least being an '08 you can have the speedo adjusted via a tune.

From what I know, some serious wheelers call the G80 the gov-bomb and when it does blow, they're stuck getting out with just the front diff working. I've also seen my son's Silvy G80 blow up just from one wheel on ice and the other on solid asphalt on the road. Another one I've seen where a Suburban was just doing a one wheel peel in snow with it's G80 refusing to engage. When it works, it works, but when it doesn't...

I can't advise on any of the aftermarket lockers. Have you tried our sister site ORTB? There may be more info there regarding off-road stuff.

Good looking rig BTW :thumbsup:

Thanks for the compliments guys.I absolutely love this truck. It's done duty as a daily driver, a spare vehicle, been mothballed, and now getting upgraded for more offroad use. She rolled over to 100,000 miles last April and only has 102K today. Everytime I drive it I turn more heads than a chiropractor.

The gears for the front diff are from Motive Gear. I "think" they and Sierra are the only manufacturers still making gears for the 7.2" front diff.
All ring and pinion manufacturers make 4.56 gears for our 8.6 rears. That's why I'm swapping from the factory 8". More options and added strength. Probably also step up to 35" tires when these wear out. As soon as the gears are in the truck I'll send the ECU out for a tune and to correct the speedo.
 

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Mooseman

Moderator
Dec 4, 2011
23,693
Ottawa, ON
If you want a good tune at a good price, our very own @limequat does it for just $99. He knows these engines inside out and can tune it to your liking as well as the speedo.


It's good to know someone is making gears for our front diff. Not easy to set up though with that case.
 
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