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2005 chevy trailblazer_ls
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Discussion Starter #1 (Edited)
Hello all, I'm hoping to get some axle swap advice. from one of the many "GURUS" :hail: here. I am replacing the engine in my 05 TB 4X4 for no compression. See this post if you want a good read: :bonk:http://forums.trailvoy.com/showthread.php?t=78064

Anyway. Since I upsized my tires when I first purchased the truck I have always complained about the lack of torque. Especially when towing my travel trailer or any tall trailer. My original thought was go back to stock diameter tires the next time I need them, however at the time of the engine swap the front differential needs removed so the work is done. That got me thinking dangerously!

I called the local salvage yard and asked if they had 4.10 front and rear diffs. I currently have 3.42 with 30.9" tires. They said yup we do $550 each.
He gave me the PN for the front and the RPO code for the rear.
Can anyone verify these numbers? Will these work for a standard length TB?

Front: 15931325
Rear: option code NA3

I dont know if the rear also contains the G80 option or not? and they couldn't tell me I'm not really sure what applications used the 4:10 and what to expect???????

Also is there anything else needed? drive shaft yoke? driveshaft mod? I'm sure I will have to reprogram the PCM??? Any PCM suggestions since the truck is down for a week?

My thought is: If I'm spending the money to replace the motor and I can save the labor to do a front differential, it is the ideal time for this upgrade if it will work. Also the rear includes rotors/calipers/axles/pads if needed.

Thanks for any and all input. I'd like to make a decision and get these Tuesday if it all comes together!

I will also add: Both the front and rear differentials although from a salvage yard have ZERO miles on them. They are BRAND NEW never installed. So that really added to the temptation!

:thx
 

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2002 envoy_slt
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45 Posts
the rpo on the gears is not right.
gu6=3.42
gt5=3.73
gt4=4.10
i may have 3.73 and 4.10 codes mixed up could sombody double check me. if it gas g80 it should say in the glovebox.
 

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2005 chevy trailblazer_ls
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251 Posts
Discussion Starter #4
Ok some clarifications from the salvage yard:


Another option code is GT5 which is for the gear ratio.
8.5" ring gear.
10 bolt cover
4.10 ratio
This does not have the G80 positraction.

I'm not so concerned about the G80 option as I am about torque in general.

Could it be that the 4.10s came with G80???
Whats the retrofit for this into a standard TB SWB?
:thx
 

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2002 chevy trailblazer_ltz
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912 Posts
If you are upgrading you rear axle, try to find one from a LWB so you can get the stronger 8.6" ring gear. As stated The RPO codes for the gears are:
GU6-3.42
GT4-3.73
GT5-4.10
 

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2005 chevy trailblazer_lt
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2,636 Posts
I'd rather the G80 over the torque, but that's me. If you off road, you want it.

Nice call on replacing it all at once, and cool pictures of the axles/diffs.

Good thing about the 8.6"/8.5" is that you have alternate options for lockers down the road.
 

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2005 chevy trailblazer_ls
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Discussion Starter #7
I was hoping that the 4.10 was used in something like the SS where its a no brainer that it had the G80. Towing tall trailers with big tires and hi gear ratios has been a huge frustration and may have lowered the actual engine life...

I'm not to concerned about fuel economy, I know I'll loose some but I'll save the new engine and I can maintain constant highway speeds.

After reading Roadie's threads it looks like the 8.6 is a exact bolt in. So I can do the PCM and be done.

Yes I'd like to have the locker, maybe one day... But the Engine,Front diff, Rear diff and labor have all put me to my $$$ limit for one go around.

Actually the final cost with labor and transportation home from KY will exceed what I paid for the truck 18 months ago. (Minus tires and wheels)

On the upside I will have what I need to do what I need. And I know what I have. Truck with a 4k mile motor and zero mile diffs.

Thinking tranny and transfer case now... They don't have either of those in such low miles so that will be when it happens to need it. My last 4L60E trans went 230k miles with a cooler and regular trailer towing so I have "some" confidence.
 

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2003 gmc envoy_slt
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Just an FYI, the SS has posi, not the G80.

Also, it seems unbelievable that anyone would order 4.10 gears without the G80. :m2:

One other thought: What size wheels do you have? If the new axle assembly is the 8.5"/8.6", do they have the bigger rotors? Will they fit with 16" wheels?
 

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2002 chevy trailblazer_ltz
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I thought the bigger rotors were only on the front end, not the rear.
 

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The 8.5 (8.6) axle is used on the extended trucks and the trucks with V8s

On the extended trucks, the rear rotors are bigger than the rear rotors on the short trucks.

I don't know if the short trucks with V8s have the larger rear rotors, or not. :undecided
 

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2005 chevy trailblazer_ls
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Discussion Starter #11
Does anyone know what I can expect for MPG with 4.10 gears and 31" tires? I had a ZR2 Blazer with 3.73 and 31" Got about 14 Hwy. The TB motors are much more efficient so I would hope for something close? Any comments appreciated.
 

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2005 chevy
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mileage

I have an 05 EXT LT with 100KMS on the 4.2 and the 4.10 g80, Stock 17'' with wrangler ats tires. When I dont have my foot into it going to a call and I have my cruise on at 100kms(60mph), my trusty mpg gauge tells me I average 19-21 MPG.
In town I get about 14-16mpg.

Where did you get the diffs and motor? I was looking online at a place called Nordstrom for super clean parts.
 

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2006 chevy trailblazer_lt
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Check this post for the motor vendor: http://forums.trailvoy.com/showthread.php?t=78064

I'm going to keep the differential vendor a secret for now... I want to make sure I get my order in first...

Thanks for the input on MPG!
Don't forget the 3 channel/4 channel ABS crossover year. Starting 2006+ our platform got a 4 channel ABS system so the rear axles are slightly different from the 2005 and earlier.

I know from personal experience if using 2005 or earlier axles in a 2006+ you lose the ABS system entirely. I'm not sure about the other way around but I think the results will be the same.

Note: the 2006+ axles have the ABS sensors close to each brake rotor. The 2005 and earlier have a single sensor somewhere else.

AG
 

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Discussion Starter #15
By what I have read and can tell the 3 channel uses a rear speed sensor located in the transfer case. I ordered them today, they will be here tomorrow. New engine showed up today, like new, so new not even paint worn from pulleys.
 

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Discussion Starter #16
OK Axles are on the way to me so its safe to share where I got them. And they have plenty more. ZERO Mile Surplus front and rear 4.10 gear 8.6 Rear ring gear

Stricker Auto Parts
Phil
800-582-5405 ext 144
[email protected]
 

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2002 chevy trailblazer_ls
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162 Posts
Dont mean to hijack the thread, but can i just go out and buy a 4:10 or 3:73 rear axle and bolt it up?
 

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Discussion Starter #18
Dont mean to hijack the thread, but can i just go out and buy a 4:10 or 3:73 rear axle and bolt it up?
Yep you can or front and rear if you have 4 wheel drive.
Point in the thread was for me to find those answers and to share with all of you on a great source for the parts.
 
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