AWD System Question

[SolidusJ]

So after 2 years in a 4WD truck and now back in AWD system, I have a few question.

I believe the 3's run full time split 40/60, I wanted to know does wheel speed and traction some how change this at anytime? I know when it's in normal AWD, the wheels change power distribution to alleviate wheel chirp when making taking turns unlike when your in 4WD high and the front axle is locked out.

That's why a lot of guys with Lincoln lockers (welded gears) usually haul out their trucks out to the trails to have a cheap full time locked out axles. The tires would be eaten up on the normal road after so many turns.

What I'm trying to get out of all this is that I'm planing to buy a Colorado cast iron differential extension tube that has a actuator to lock and unlock the front axle.

Some of the 355 guys have done this to have the cast iron diff so I know their extension tube will bolt up without a issue. With an unlocked fornt end, there wouldn't be any drag on the front end right? I know the T-case will always spin but now some MPG might be able to get picked up without all 4 wheels getting power to them all the time.

Am I way off base with my thought process or is this something that might work? I'm worried that the ABS system will pick up on the front axle not getting any power and tripping limp mode on the truck.

Down below is a picture of a cast iron diff with a Colorado differential extension tube.

 

[deserth3]

I'm no expert. They say with enough money and duck tape anything will work.
My guess is you'd have to drive it in 4hi lock.
In normal 4 hi with this system it would act like the front drive shaft is removed. The transfer case acts like and open diff and sends power to the axle with the least traction. Which would be the front with out the shaft installed.
In 4 hi lock. Power is sent 50/50. And you could drive like normal. There are some difference of opinions on whether you'd increase MPG or not.

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[SolidusJ]

I'm no expert. They say with enough money and duck tape anything will work.
My guess is you'd have to drive it in 4hi lock.
In normal 4 hi with this system it would act like the front drive shaft is removed. The transfer case acts like and open diff and sends power to the axle with the least traction. Which would be the front with out the shaft installed.
In 4 hi lock. Power is sent 50/50. And you could drive like normal. There are some difference of opinions on whether you'd increase MPG or not.

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What I'm taking away from this is pretty much like the solid axles when you lock and unlock the hubs. When you lock them you send power to the axle and now the engine is working more to send power to that axle.

With the 3's, if we are able to unlock the axle it would spin freely which in turn less power being sent to it. The t-case will still spin the diff but now power isn't being sent to each wheel.

Now I do understand what you mean by saying the 3 would have to run in 4hi to send the correct amount of power to the rear axle to move it. This is all a thought and what's the worst that could happen? It works and now there's a small chance to pick up some MPG?

Thank you for your input.

 

[Bruces]

I believe the colorados and canyons also have a different transfer

 

[4speedfunk]

The 2wd axle really needs a 2wd t-case to work with it. To make a true 4x2...you must shut off both the hubs and the front output of the t-case. This will allow you to drive down the road with a motionless front diff.
Failing to do either (disconnect hubs or front output), and you will still have a spinning diff.
Most modern 4wds (including ALL the part-time GM IFS trucks since 1992) have permanently connected hubs, so they cannot truly shut off completely. Instead, they shut off the front t-case output, and disconnect one side of the front axle via the CAD (center axle disconnect). This allows the spiders inside the diff to freely spin...even though the diff and gears are motionless. There is almost zero drag from the spiders, so disconnecting hubs are not needed with a CAD.


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[SolidusJ]

The 2wd axle really needs a 2wd t-case to work with it. To make a true 4x2...you must shut off both the hubs and the front output of the t-case. This will allow you to drive down the road with a motionless front diff.
Failing to do either (disconnect hubs or front output), and you will still have a spinning diff.
Most modern 4wds (including ALL the part-time GM IFS trucks since 1992) have permanently connected hubs, so they cannot truly shut off completely. Instead, they shut off the front t-case output, and disconnect one side of the front axle via the CAD (center axle disconnect). This allows the spiders inside the diff to freely spin...even though the diff and gears are motionless. There is almost zero drag from the spiders, so disconnecting hubs are not needed with a CAD.


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I thought with the extension tube that has a actuator would in turns unlock the axle/hubs seeing how we don't have the manuals hubs. Like with solid axles when you have to lock the T-case and jump out and lock each hub?

What I'm thinking is with the axle unlocked, the t-case would still spin the diff gears but wouldn't send power to each wheel?

Another thing I think about is we could do the same by removing the CV's from each side to reach the same goal by.

Even if we were to remove the front driveshaft, the front axle would be locked and cause drag, right?

I remember back when I was thinking this same thing a few years ago, there's no way to unlock the T-case because the each output shaft is set in by gears.

I'm that kind of person that has a hard time getting out what I'm trying to say so it would be better to make it happen in person or something? Ugh...

Now that I lock at the picture, I can see what you mean about the passenger side wheel would still spin and the actuator would unlock the driver wheel only.

 

[4speedfunk]

The CAD is a sort of a "get around" device that Jeep pioneered in the 70s. They've been made with vacuum, cables, levers, and most often...a solenoid like the Colorado uses. Pretty much every manufacturer has adopted the solenoid, Dodge, Jeep, Ford, etc because it's much more reliable than the old vacuum type.
The CAD doesn't "unlock" anything. It simply disconnects one side of the diff. from the spinning wheel on the other end of it. The CAD is electrically activated when you put the t-case into 2wd. The result is that diff and front driveshaft both quit spinning. It's at this point where the spider gears spin like hell inside the non-spinning diff. This is only possible because one side has been disconnected. This is how nearly all modern part-time rigs get 2wd without locking hubs. Basically...the industry figured out that disconnecting one side of a diff and spinning spiders all the time is okay...has minimal drag...and doesn't require the driver to manually unlock hubs. Additionally, it allows the use of sealed unit bearings at the hubs...much cheaper and requiring less maintenance than old school locking hubs.


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[SolidusJ]

The CAD is a sort of a "get around" device that Jeep pioneered in the 70s. They've been made with vacuum, cables, levers, and most often...a solenoid like the Colorado uses. Pretty much every manufacturer has adopted the solenoid, Dodge, Jeep, Ford, etc because it's much more reliable than the old vacuum type.
The CAD doesn't "unlock" anything. It simply disconnects one side of the diff. from the spinning wheel on the other end of it. The CAD is electrically activated when you put the t-case into 2wd. The result is that diff and front driveshaft both quit spinning. It's at this point where the spider gears spin like hell inside the non-spinning diff. This is only possible because one side has been disconnected. This is how nearly all modern part-time rigs get 2wd without locking hubs. Basically...the industry figured out that disconnecting one side of a diff and spinning spiders all the time is okay...has minimal drag...and doesn't require the driver to manually unlock hubs. Additionally, it allows the use of sealed unit bearings at the hubs...much cheaper and requiring less maintenance than old school locking hubs.


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I get it now, and there's nothing we can really do about the t-case.

 

[4speedfunk]

Well. Maybe.
06H3 & I have discussed the mating a Colorado/Canyon t-case with an H3 t-case. The idea is to replace the H3's variable full-time 4wd shaft with the solid part-time 2wd shaft from the CC. This would convert the 4HI-Street variable mode to 2HI-locked...like a traditional t-case. Obviously a big reason for this is to keep the H3's awesome 4:1 low range but dump the variable full time 4wd high range.
Another option would be to install the 4:1 low range gear set into a part time CC t-case. Either way, the idea is the same...to get a traditional 2HI-4HI-4LO that works with the buttons on the dash and bolts up like a stock one.
If we could figure out how to do it...it would really benefit us SAS guys that already have lockout hubs on our front axles. For the IFS guys...it would require a CC front axle swap (with the CAD) like you proposed in your original post.

This is all talk of course. I have yet to disassemble a CC and H3 case side-by-side to see if it can be done. One thing 06H3 & myself agree on is that the 4:1 low trumps any sort of 2wd mode. If we have to choose between the 4:1 low and 2wd...we will choose the 4:1 full time case every time.

 

[4speedfunk]

I keep waiting for 06H3 to pop his t-case. That would give us the excuse to pursue the idea further. I don't think either of us craves 2wd enough to dive into the project, and tear apart a perfectly good Hummer case to experiment. All that would change if something breaks.


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[atvspeed4]

This discussion used to come up on the S10 Zr2 forum all the time as we used to explode the front axle disconnect all the time and swap out with a solid AWD shaft from a bravada while still running the stock 2wd transfer case. I tracked my mpg difference before and after and only noticed a 0.15 mpg increase by running stock setup with CAD vs 2wd transfercase with solid front axle shaft. Not worth introducing new weakness to ifs for that gain. We are currently running a 2wd np241 with ifs and there are no issues at all with traction control or stabilitrac.

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[Happy Hummer]

Lol! Here were discussing how to add CAD to the front axel while in the XJ forum for Jeep there discussing ways to get rid of it.

 

[4speedfunk]

True. The CAD is not something I would want on IFS or an SA. Mileage is of no concern at least for me. I want the 2wd so I can save wear & tear, and shut off the front if it breaks on the trail.


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