Offroad Trailblazers and Envoys

i want a locking diff!

Dumping ground for offroad Trailblazer or Envoy general discussion.

by jrivs4x4tb » Tue Jul 01, 2014 11:55 pm

Alright so being new to the offroading life I had no clue what kind of different was good, when I bought my tb I definitely didnt know that it had an open rear diff (gu6 3.42 ratio , no g80code :pale: ) so now obviously I want the rear diff to be a locking one, so what are my options I know I can go swap the whole rear end from a junked tb that has the g80, but that is difficult to find in my area and to me seems a bit excessive seeing as I can probably just order some parts online and just swap out internals ... Or can I? I read that I probably have the 8" housing which supports little to no aftermarket parts... I'll have to look at it myself later, but basically I want to know what others in my situation have done, I'm looking for cost effective options but nothing I'll regret not spending the extra money on later . Also would this require changing the rear bear ratio ? Which from what I understand would require me to also change the front to match up...

Also I don't think I'll be doing a whole bunch of Rocky surface traveling so maybe a limited slip would suffice , or is it just worth more in the long run to get a full locking dif?

I know I can research all this myself but I prefer direct advice because of course everyone's preference and needs are different and I do like a good conversation. And if any of you are in the Colorado springs area then we sure as he'll can meet up and find some trails I need offroading buddies! I'm in the army at fort Carson , originally from Arizona so if there are any az dwellers then by all means hit me up
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by harvyne » Wed Jul 02, 2014 3:07 am

i was researching a g80 upgrade at some point and read that if you dont have good knowledge on rebuilding rear axles its not a good idea as its quite extensive, to have a proffesional do it i think it quoted at least a $1000 or more job. Do a google search and youll find out what you need, it was an ORTB article from one of us here. Personaly if im ever to do it i will just do a rear end swap as its cheaper and quicker from what i gather. I would not worry about it until that point comes where you know whether or not you need it. IMO.
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by navigator » Wed Jul 02, 2014 8:06 am

there really aren't any locker options for your 8" rear.

your best bet is an 8.6 from an EXT or V8 model.
You can get one with a G80 (locker), G86 (limited slip) or open and swap in your own locker. If you go with something like a Powertrax, it uses you own carrier so you don't have to reset the gears.

Your plan for tire sizes will determine if you need to re-gear. If you have the I6, 33s should have 3.73 or greater, 35s should have 4.10 or greater. MOst folks running 3.42s moving to 33's go ahead to 4.10s since they have to swap the front diff anyway.

The gear calculator tool can give you ideas about gears/rpms/tire sizes
http://www.offroadtb.com/articles/tech- ... alculator/.
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by Eredin » Wed Jul 02, 2014 10:24 am

I've also found that even running 32's, the 3.42s are inefficient and it's very difficult to keep the TC locked. This could be the cause of an ailing converter, but you'd see much better response going with more appropriate gears. I'm on the lookout for a set of 3.73s, locally, to see if I can get a good deal at some point. Just be weary.
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by Trail X » Wed Jul 02, 2014 11:48 am

jrivs4x4tb wrote: . Also would this require changing the rear bear ratio ? Which from what I understand would require me to also change the front to match up...

I'm not sure about the bear ratio, but the gear ratio does not HAVE to change in order to get a G80. You just have to be mindful of the gear ratio on your truck, and get a new axle to match. If you're just going to swap in a G80, you can just reuse the gears in your truck. Swapping in a G80 shouldn't be too hard, but you need to be sure to check your backlash and pattern. More than likely it will be ok, but they need to be checked. Pulling the pinion is the annoying part of regearing, and you won't have to do that for a G80 swap.

If you do a whole axle swap, it would behoove you to look at your gear ratios and the tires you plan on putting on, and doing a gut check to see if your current gears will suffice for your mission. If you're swapping in a rear axle already for a locker, you might as well get the gears that you want in the future. It will only require swapping the front diff too, which is a bit more work, but not impossible to do yourself.

jrivs4x4tb wrote:Also I don't think I'll be doing a whole bunch of Rocky surface traveling so maybe a limited slip would suffice , or is it just worth more in the long run to get a full locking dif?


Limited slips are available in the 8.6 and the 9.0, and rarer than the G80 as I understand it. It requires a whole axle swap.
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by jrivs4x4tb » Wed Jul 02, 2014 12:11 pm

Ok well I will see what is available for me here in Colorado, I might just do the lift and new tires and some skid plates and rock sliders and see if I really need to upgrade to a locking diff, I've already hit some good trails and had absolutely no problem maintaining traction so it may just be unnecessary, and who knows the previous owner could have added a locking one but kept no record... So I'll have to look, because in 4 Wheel drive the vehicle takes sharp corners a lot harder than my buddies envoy that has an open diff .. from what I understand a locker will make turns go slower . Is this true? And to me it looks level so maybe there is a leveling kit already on I haven't had time to really look as I'm in the army and am always busy,

Thanks everyone for the feedback and please continue giving me tips if you can
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by DirtyBacon04 » Wed Jul 02, 2014 12:53 pm

Pics will help a lot. I doubt the previous owner added either a locker or a lift/level. These trucks already are pretty level, usually.

The Detroit Tru-Trac (LSD) is available in the 8" which I imagine would work well if you're not hardcore. Plus if you know the secrets of left-foot braking or E-brake riding, the Tru-Trac is a pretty viable option. (and cheaper). I wish I could put one in my front diff, but that's not the point.

The Powertrax NoSlip (available in 8.6") has worked wonders for me in the past 2 trips.
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by jrivs4x4tb » Wed Jul 02, 2014 9:07 pm

Yeah well whatever the case I'm definitely going to add some sort of aftermarket diff but first I will do the 3" rear and 2.5" front lift
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by Shdwdrgn » Fri Jul 11, 2014 2:30 pm

Erg... I was going to offer you my original GU6/G80 rear, then I noticed you have a 2006. I'm never going to get my old diffs sold, am I?
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by jrivs4x4tb » Fri Jul 11, 2014 3:24 pm

It won't fit? I'd buy it
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by Trail X » Fri Jul 11, 2014 3:25 pm

The ABS isn't compatible. 3 channel vs 4 channel.
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by Shdwdrgn » Fri Jul 11, 2014 3:39 pm

Yeah, what he said. You missed it by a year. Mine will only work for 2002-2005. Now if you want to look at my *front* diff, that will fit. (Does the front diff have the locker also? My truck came with G80, so I assume the front has it too).
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by TBYODA » Fri Jul 11, 2014 3:45 pm

Shdwdrgn wrote:Yeah, what he said. You missed it by a year. Mine will only work for 2002-2005. Now if you want to look at my *front* diff, that will fit. (Does the front diff have the locker also? My truck came with G80, so I assume the front has it too).
I don't believe so from what I have read, all fronts are open. To be honest surprise you said that. :finger:
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by Trail X » Fri Jul 11, 2014 3:54 pm

G80 option is rear locker only. All stock front diffs are the same across the board except for gear ratios.
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by Shdwdrgn » Fri Jul 11, 2014 3:59 pm

Grrrr... I think I paid extra trying to find a 410 front diff with the G80 option. Then again, maybe not. They were pretty scarce when I was searching, took me three months to find one that didn't have 200k on it.
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by jrivs4x4tb » Fri Jul 11, 2014 4:09 pm

Is the abs interchangeable? Like could I take mine off and put it on the g80 haha I have no clue how abs works, and do I even need abs I mean I've had vehicles without it doesn't seems to help much
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by navigator » Fri Jul 11, 2014 4:22 pm

2006+ have the 2 ABS sensors, one at each end of the axle tubes.
I think the 2005 and earlier had one sensor on the diff housing (or similar).
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by jrivs4x4tb » Fri Jul 11, 2014 4:26 pm

I'm sure there is a way to ghetto rig it to where it works, I'm pretty good with electronic components so who knows
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by v7guy » Fri Jul 11, 2014 4:47 pm

The 3 channel has the sensor at the transfer case, the 4 channel has the sensor at each wheel.
In other gm reluctor wheels (like the LS reluctor for LS motor timing) the sensor reads on the leading edge of the tooth. Nobody has determined what the abs sensor is actually reading off of. I have found that the abs reluctor wheels in multiple GM trucks/hubs have the same number of teeth, but I dunno if that translates to they can all run on the stock abs controller.
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by Shdwdrgn » Fri Jul 11, 2014 4:50 pm

All models have a sensor on each front wheel. The 02-05 have a single sensor at the back of the transmission which is used to calculate the rear wheel speed. The 06+ have actual sensors on each rear wheel. There is a significant difference in how the PCM handles each model, so you're not going to be able to just rig something up that would still function correctly. (However I wonder if the sensors could be removed from the original rear axle and added to an older axle? No clue if that's possible.)

Really you're better off just finding an axle from an 06+ EXT, then you have the heavier 8.6" diff and you're ready for any mods you want to make in the future.

By the way, in regards to your original post... I've done some light/medium wheeling with my original setup, plus of course lots of snow driving, and the G80 works fantastic for all conditions around here.
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