G80 Swap 4.2L I6

[crate2002]

Since I am new to this, I have discovered my TB in fact does NOT have the G80. Thats depressing to figure out when wanting to complete a build. So now I am wanting to do a swap. If I am correct, I have an 8" rear. It has GU6 in the glove box (3.42). What would be my best way to go about this? Whole rear swap or internals swap? I'll have to locate one that is GU6. OR would you recomend changing the gearing front and back to 4.10? Decisions... Decisions...

[Cable810]

Well it all depends on your mission. The 8.6" axle is much stronger than our factory 8" axle. 4.10s are better for bigger tires but are harder to find, 3.42s are not best for bigger tires but are much easier to find. I'd also suggest to do some reading on the G80 as its not the strongest locker. I'd swap a whole new axle assembly vs having to re-gear your current axle.

[The Roadie]

Many of us swap in 8.6" rear junkyard axles with G80s in them for a few hundred bucks. If your mission involves trails that may put the G80 at risk, there are aftermarket lockers available for the the 8.6 and the 9.5 SS rear axle. None except the Eaton G80 available for the 8.0

[TBYODA]

Well it all depends on your mission. The 8.6" axle is much stronger than our factory 8" axle. 4.10s are better for bigger tires but are harder to find, 3.42s are not best for bigger tires but are much easier to find.

Another option but some what more costly but you will know what you are getting. Is to get the cheapest 06+ 8.6 3.42 rear end you can find and buy front and rear gears, along with new seals and maybe new bearings if needed. You of course have to get the new gears set by someone that has do it before or shop.

rear end 4:10

front IFS 4:10

[crate2002]

So if I am understanding correctly, 8" should be swapped out with something bigger. OEM locker for trail is not that strong but an after market locker for an 8.6" swap would be more reliable?

[crate2002]

Well it all depends on your mission. The 8.6" axle is much stronger than our factory 8" axle. 4.10s are better for bigger tires but are harder to find, 3.42s are not best for bigger tires but are much easier to find.

Another option but some what more costly but you will know what you are getting. Is to get the cheapest 06+ 8.6 3.42 rear end you can find and buy front and rear gears, along with new seals and maybe new bearings if needed. You of course have to get the new gears set by someone that has do it before or shop.

rear end 4:10

front IFS 4:10

I can look into that as an option. If I were to do an 8.6 swap with an after market locker, I guess then would be the time to change gear ratio's front and back. A good question is, how big of a tire will the 3.42 turn before the TB starts to hate life? 30"? 32"? I realize this swap will take some $$$ but better to be done right than be broken down on the trail

[navigator]

I run 32's with 3.42s and it is fine most of the time.
Towing my bass boat in the summer in OD the tranny warms up more than I like, I've seen it as high as 228. Dropping back down to 3rd helps the tranny temps.
I live in the flat lands of NC though.
I likely would have been satisfied with 3.42s permanently with a tranny cooler installed.
I chose not to run 33's with 3.42s for fear of overheating the tranny.
I ran across a deal though and have a set of 4.10 axles waiting for me to install.

[TBYODA]

I can look into that as an option. If I were to do an 8.6 swap with an after market locker, I guess then would be the time to change gear ratio's front and back. A good question is, how big of a tire will the 3.42 turn before the TB starts to hate life? 30"? 32"? I realize this swap will take some $$$ but better to be done right than be broken down on the trail

I am in the same boat as you, 3.42 gears open diff. Hind sight is 20/20 if you know what I mean. Max with 3.42 is 32" but I'd add external tranny cooler any how. Some say you could do 33" with a cooler but I am not sure about that and how long your tranny would last. Take a look at the chart below it will help understand. Tire Size Calculator

Depending on your mission you could run this in the 8.0,Eaton Detroit Truetrac Differentials however most would suggest just upgrade to 8.6 with G80 because it would be cheaper and stronger in spite of G80 issues. I am still on the fence with all of this myself but have been doing a ton of research. At the moment I am kinda leaning on the side of getting a open 8.6 3.42 and putting a lunch box locker in it and re-gear at a later time because of the cost. HardtrailZ (Kyle) has kinda push me to that side from different threads.

[HARDTRAILZ]

Truetrac is limited slip, not a locker. Something I would only really consider for a front diff, but they are not offered to us for ours.

There are several discussions I would think you should read on this site and others regarding open/LS/Lockers, plus gearing. We have a limited number of options and several opinions as to what is best. Help us help you....

What tire size are you looking to run?
Mostly on-road or off-road?
How difficult of off-road? Trails or rock gardens or some dirt roads or sand?
Pull trailers?
Spend alot of time on the insterstate?

[TBYODA]

Truetrac is limited slip, not a locker. Something I would only really consider for a front diff, but they are not offered to us for ours.

And that really sucks It would be good combo.

[crate2002]

Truetrac is limited slip, not a locker. Something I would only really consider for a front diff, but they are not offered to us for ours.

There are several discussions I would think you should read on this site and others regarding open/LS/Lockers, plus gearing. We have a limited number of options and several opinions as to what is best. Help us help you....

What tire size are you looking to run?
Mostly on-road or off-road?
How difficult of off-road? Trails or rock gardens or some dirt roads or sand?
Pull trailers?
Spend alot of time on the insterstate?

To put some light on what I do with my tb, Ill list them below for some better understanding...
-It is my daily driver / family car
-31" tires on it right now (Kelly Safari TSR's)
-Trails I have gone on were not TOO aggressive but I was hoping to one day attack the rocky trails (Paragon in PA) jeep place that is pretty rocky. No sand, there is none near me
-Mostly used on road
-I haul a trailer with 2 quads on it every other weekend for 3 hours round trip
-Interstate is MAYBE once a year for vacation. Just local highways and back roads near home

I saw there is concern for Trans overheating. Again as a rookie, I never knew that was an issue. I guess I should take care of that issue asap as the roads I take to ride quad are UP HILL to the destination 1.5 hours north from my home

[HARDTRAILZ]

The trans overheating is sort of an issue. Some people blow it out of proportion, but an aftermarket cooler is cheap and easy to install. One of those things better to have and not need, than to need and not have.

I went years with 3.73 in heavy 33s and shit for aerodynamics without only getting the trans hot once in the mountains. 99% of the time it was fine and it was easy enought to baby it and keep temps ok once I saw them rising.

I did add a Hayden cooler before I jumped up to 4.10s and 35s. Since the cooler the mountains and everything else has been a non issue.


Are you wanting bigger tires or just the increased traction of a locker? If you are not going bigger and are happy with current performance...just find a cheap g80 3.42 rearend. Complete will be better in either 8.0 or 8.6 . Go to 8.6 if price close, but for your use...an 8.0 ought to be fine. Mine was for way harder abuse than you are doing.

[navigator]

if you have an android bluetooth phone/tablet you can download an app called torque pro and get a bluetooth OBDII adapter (like ELM327 from ebay) and set it up to read tranny temps and lots of other items. There are a lot of folks on here that run them.

If you are like me and don't have an android phone, you can get a scangauge II to read the temps.

As Kyle mentioned it is good insurance to just get the cooler.

[crate2002]

if you have an android bluetooth phone/tablet you can download an app called torque pro and get a bluetooth OBDII adapter (like ELM327 from ebay) and set it up to read tranny temps and lots of other items. There are a lot of folks on here that run them.

If you are like me and don't have an android phone, you can get a scangauge II to read the temps.

As Kyle mentioned it is good insurance to just get the cooler.

I have an iphone found this on the app store. Works with a wifi adapter

https://itunes.apple.com/us/app/engine-link-obd-ii-vehicle/id591557194

If you want to See what your car is doing in real-time, get OBD fault codes, car performance and sensor data, have this app handy and it will turn your iPhone/iPod into vehicle / car performance / diagnostics tool and scanner that uses an OBD II WIFI adapter to connect to your OBD2 engine management / ECU.
+ Show and reset a DTC / CEL / fault code like a scan tool
+ Graph data
+ MPG widget to plot real time fuel efficiency
+ Heads up display / HUD mode for night time driving (mirror the display on your vehicle's windshield)
+ Can read Transmission Temperatures (vehicle dependant)
+ Horsepower/HP & Torque / acceleration
+ Boost / vacuum gauge
+ Engine speed / Engine RPM / Engine Load /Coolant / Fuel Tank
+ Customizable dashboard
+ Full configurable GUI with user choice of dial gauge, bar gauge, plot gauge, digital gauge, and on-off gauge as display elements
+ Full custom PID support. Formula support. Preloaded standard PID library and Prius PID libraries. User can add more libraries within the app or by using iTunes File Sharing
+ Multiple ECU support. Non-CAN, 11-bit CAN, and 29-bit CAN ECU bus types
+ Multiframe data support
+ Background color option
+ Preloaded GM and Ford PID libraries

[crate2002]

Are you wanting bigger tires or just the increased traction of a locker? If you are not going bigger and are happy with current performance...just find a cheap g80 3.42 rearend. Complete will be better in either 8.0 or 8.6 . Go to 8.6 if price close, but for your use...an 8.0 ought to be fine. Mine was for way harder abuse than you are doing.

I am maxed out with room without spacers. They are not QUITE 31"... They are 245/75R16. Exact diameter NEW is 30.47" with a crossection of 9.76"... If I do go bigger I would do 32-33"

[mikekey]

That's similar in size to what I originally had before my 35's. However I had 3.75's. I don't see why a 3.75 G80 8.6 wouldn't be just ok for 32's. Quite a few folks running just that in stock trim. I've been rolling around with 3.75 on 35's for awhile. Not recommended. I'll be going up to 4.53's after Christmas.

[HARDTRAILZ]

3.73, 3.73, 3.73, 4.56

I think those are the gears he meant to type or he has some custom shit going on.

[mikekey]

Yup. That's what I get for multitasking

[AlekG]

Haven't finished the first post on my build thread yet (sorry ... been procrastinating), but here is an excerpt with all the axle information to go to 4.56 gears with an electronic locker for the rear:

Front

• GM 7.2IFS Oil Pan Mounted Front Axle from Cathcart Auto Parts in Burford, Ontario - spare 7.2" purchased so that National4WD could set it up off-vehicle
• Yukon Gear 7.2" Ring & Pinion Set with 4.56 Gear Ratio "Reverse" GM7.2-456R
• Yukon Gear Master Overhaul Kit GM7.2IFS-C
• Royal Purple Heavy Duty Gear Oil

Rear

• GM 8.6 Rear Axle (2006+) from Carcone's Auto Recycling in Aurora, Ontario - replacement 8.6" purchased in order to use 4.56 gears, Auburn locker, and so that National4WD could set it up off-vehicle
• Yukon Gear 8.5"/8.6" Ring & Pinion Set with 4.56 Gear Ratio GM8.5-456
• Yukon Gear Master Overhaul Kit GM8.6-A
• Auburn Gear ECTED Max Electronic Selectable Locker 545004 - limited slip when off, locked when on
• Royal Purple Heavy Duty Gear Oil

One important point to remember (it may have been mentioned ... not sure) is that GM changed the ABS systems in 2006. Prior rear axles have a single ABS sensor (by the housing I believe) and 2006+ have dual ABS sensors (by the bearings). You can use an older axle but the ABS system will not work (and that annoying light will stay on in the dash )