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Discussion Starter #1
The ED is my wife's truck, i bought it for her and she loves it...I like it to.
How does the auto 4x4 function work? She was asking about using 4x4 when it's raining and I told her that 4 wheel drive is only designed for use on loose surfaces, due to binding when turning. Is this still true on newer IFS 4x4s?
How does the auto 4x4 function engage while the rear tires are spinning? Does the t-case have a viscous clutch vs a chain?
Are there any adverse effects to her forgetting about having it in auto 4x4 and driving when it's not rainy weather?
This is the first 4x4 I have owned that didn't have a handle for the t-case.
Thanks in advance.
 

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What you told her is true, for traditional 4wd LOCK, but I believe this transfer cases use a clutch system, so you can use 4x4 AUTO more like an all wheel drive system where the truck doesn't engage the front wheels until it detects slip. I've read some guys leave their truck in 4wd auto indefinitely, but others argue this negatively impacts fuel mileage, and it's a waste to leave in in 4wd auto.

Usually i would use 4wd Auto in the winter when it's lightly snowing and i might encounter slick spots, or occasionally in heavy rain. I use 4wd LOCK when I want to pull into my back yard which is a steep grassy hill and not worry about the rear slipping and tearing up the grass before the 4wd Auto kicks in.
 

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If your wife's truck has the 4 wd auto function and the 4wd lock function she can use the 4 wd auto function whenever she wishes. For myself, I would not use it in the rain since I prefer that the front wheels can use all their available traction for stopping and steering rather than going. It can also give you unfounded confidence in the traction you have and encourage driving faster than you can safely stop and steer. Ensuring decent tread depth and good quality tires seems more important to me. If she uses it she must be careful to use only the auto function. AS I understand it, lower trim trucks have a different transfer case and do not have the auto function.
 

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Discussion Starter #4
thanks for the information. we have plenty of tread left on the stock goodyear rubber, but with the torque coming on immediately it's hard to pull out into traffic without the back wagging.
we have to feather the accelerator up until 3rd sometimes with these gravel roads when wet.
I'll look for some better tires once these are worn, for now I'll have her use 4x4 auto when wet out.


...I've read some guys leave their truck in 4wd auto indefinitely, but others argue this negatively impacts fuel mileage...
Since the hubs are locked all the time, which means the front driveshaft is spinning all the time, I'm not sure how this would negatively impact fuel mileage.
I'll have her leave it in 4x4 auto and see if the mileage (or tire wear) take a hit. currently we average 25 city, 28-30 hwy.
 

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4x4 Auto has no impact on mpg. I've gotten amazing mpg driving in horrible conditions, probably because I had to drive slower as well.
 

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Discussion Starter #7
I'd be interested to know if 4x4 auto keeps the t-case clutch engaged and allows slip, or only engages the clutch when needed.
Perhaps that is the main difference between AWD and 4x4 auto.
Our 06 Durango was equipped with the Hemi, the ED towing package, and was AWD all the time, which required me to change the transfer case fluid every 30k miles.
 

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I'd be interested to know if 4x4 auto keeps the t-case clutch engaged and allows slip, or only engages the clutch when needed.
Perhaps that is the main difference between AWD and 4x4 auto.
Our 06 Durango was equipped with the Hemi, the ED towing package, and was AWD all the time, which required me to change the transfer case fluid every 30k miles.
Hey chizzle, if you search my posts you will find a bunch of information on how your truck transfers power with the transfer case. I have a FoxWell tool that gives me all of the data from the Transfer case. Basically, in auto 100% to the rear until there is slip. Something to consider is that the same transfer happens in reverse. If you are rolling down the driveway and the rear starts to slip in deceleration, it will transfer power.

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thanks for the information. we have plenty of tread left on the stock goodyear rubber, but with the torque coming on immediately it's hard to pull out into traffic without the back wagging.
we have to feather the accelerator up until 3rd sometimes with these gravel roads when wet.
I'll look for some better tires once these are worn, for now I'll have her use 4x4 auto when wet out.



Since the hubs are locked all the time, which means the front driveshaft is spinning all the time, I'm not sure how this would negatively impact fuel mileage.
I'll have her leave it in 4x4 auto and see if the mileage (or tire wear) take a hit. currently we average 25 city, 28-30 hwy.
The hubs are direct but there is a coupler in the front axle that is disconnected when in 2wd.

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I'd be interested to know if 4x4 auto keeps the t-case clutch engaged and allows slip, or only engages the clutch when needed.
Perhaps that is the main difference between AWD and 4x4 auto.
Our 06 Durango was equipped with the Hemi, the ED towing package, and was AWD all the time, which required me to change the transfer case fluid every 30k miles.
Based on my experience on the hill in my backyard, it's 100% rear wheel drive, until it detects slip, then it engages the front wheels. It's a lot like the "Realtime 4wd" on my stepdads honda element, when you are driving his car in the rain or snow, and you mash the gas to pull out in traffic you can feel the front wheels spin for half a second before the rear engages and off you go, I would get the same feeling in the grass with my truck in 4wd Auto.
 

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Discussion Starter #11
The hubs are direct but there is a coupler in the front axle that is disconnected when in 2wd.

Sent from my SM-G950W using Tapatalk
probably similar to the CAD on solid axle vehicles, lets the front two wheels spin at different speeds to prevent binding.

Hey chizzle, if you search my posts you will find a bunch of information on how your truck transfers power with the transfer case. I have a FoxWell tool that gives me all of the data from the Transfer case. Basically, in auto 100% to the rear until there is slip. Something to consider is that the same transfer happens in reverse. If you are rolling down the driveway and the rear starts to slip in deceleration, it will transfer power.

Sent from my SM-G950W using Tapatalk
Thanks for the clarification. I think we'll keep in in 4 AUTO when it's rainy out from now on.
 

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4wd auto is a dangerous option, by the time the slip is detected you could end up in a ditch. I just use 4wd lock when needed.
 

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4wd auto is a dangerous option, by the time the slip is detected you could end up in a ditch. I just use 4wd lock when needed.
If you are driving it to the point where 4wd auto is a dangerous option, I would seriously consider your driving style and or skills.

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Discussion Starter #14
If you are driving it to the point where 4wd auto is a dangerous option, I would seriously consider your driving style and or skills.

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What I was thinking also.
 

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I want the wiring harness and switch that provides 100% clutch lockup to the front end. Anyone have one and can point me to the seller?
 

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The individual with the switch kit is Brandon.

Now to confuse some people and contradict some others.

If your t-case has auto 4wd and 4wd loc in a RAM your case works as follows;
also there are a lot of threads on these t-cases.

In 2wd all power goes to the rear wheels,
the front axle disconnect is disconnected.

When this transfer case is engaged and applying power to the front axle in any mode there are several components involved.
It has an electrically activated wet clutch, and a ball ramp device.
When this case is engaged the electric clutch receives a variable voltage signal from the computer to engage some what.
When the rear wheel speed exceeds the front wheel speed the ball rolls up the ram added compression to the wet clutches,
as long as the rear wheels are on a surface with sufficient traction for the drive train to apply torque to the ball and cam the clutch
will work fairly well.
The main trouble is when the rear wheels have very little or no traction there is no torque developed to tighten the ball and cam into the clutch pac
which results in slippage and overheating of the transfer case.

With the vehicle in gear, (drive or reverse) In 4wd auto the computer engages the front axle disconnect (the modern locking hubs) and monitors
the rear wheel slippage when it starts to slip it will send a signal to the clutch pac to start to engage, it will modulate that signal as it feels fit to,
and with the clutch pac engaged the ball and cam can and will clamp the clutch pac as well as it can. It it senses no difference in wheel slippage it will remove the
signal from the clutch pac.
It will repeat this process as long as you are in 4wd auto, it also cuts off the signal to the clutch pac at various turn angles of the front wheels.

In the similar manner when 4wd loc the front axle coupler is engaged and a voltage signal is sent to the clutch pac (supposedly it is a higher voltage) when the
computer decides it should also when slip is detected in the rear wheels. The rest of the function is the same as auto, so the only difference is a slightly more aggressive signal to the clutch pac when in loc as compared to auto.

This system will disengage the clutch every time the transmission is placed in park, even with the t-case still in 4wd.
So on a hill covered with wet slippery snow if you stop to get out of your vehicle when you place it in park you are in 2wd and
when you release the brakes the truck can and will slide in 2wd.

As far as I am concerned this is a fair weather transfer case that will work OK for most people for highway travel.
I know for a fact that my 2015 behaves almost the same in auto as it does in 4wd loc, you can drive it in figure 8's on pavement with no crow hopping or jerking from
the front axle.
In either mode if you try to back up a wet grassy hill your rear wheels will spin a bit before your front one start to work and this will occur every time you release the throttle if you are backing up to something on wet grass or a slippery surface every time you start and stop your rear wheels will spin and dig a bit before the front wheel do anything.
In moderate or good traction situations were 4wd drive is needed this system will work very good. As an example pulling a loaded trailer up a grade on a gravel road and turning onto a paved road you can use 4wd auto or loc and this system will do a good job and you can switch it to auto or 2 wd while accelerating on the paved road.

In 4wd lo loc this case functions the same as 4wd loc with a few minor computer differences and a considerable gearing difference.

The switch kit from Brandon W applies full voltage to the clutch untill you turn it off it makes this case work much much better in low traction situations.

Sorry for such a long post
Lou
 

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The individual with the switch kit is Brandon.

Now to confuse some people and contradict some others.

If your t-case has auto 4wd and 4wd loc in a RAM your case works as follows;
also there are a lot of threads on these t-cases.

In 2wd all power goes to the rear wheels,
the front axle disconnect is disconnected.

When this transfer case is engaged and applying power to the front axle in any mode there are several components involved.
It has an electrically activated wet clutch, and a ball ramp device.
When this case is engaged the electric clutch receives a variable voltage signal from the computer to engage some what.
When the rear wheel speed exceeds the front wheel speed the ball rolls up the ram added compression to the wet clutches,
as long as the rear wheels are on a surface with sufficient traction for the drive train to apply torque to the ball and cam the clutch
will work fairly well.
The main trouble is when the rear wheels have very little or no traction there is no torque developed to tighten the ball and cam into the clutch pac
which results in slippage and overheating of the transfer case.

With the vehicle in gear, (drive or reverse) In 4wd auto the computer engages the front axle disconnect (the modern locking hubs) and monitors
the rear wheel slippage when it starts to slip it will send a signal to the clutch pac to start to engage, it will modulate that signal as it feels fit to,
and with the clutch pac engaged the ball and cam can and will clamp the clutch pac as well as it can. It it senses no difference in wheel slippage it will remove the
signal from the clutch pac.
It will repeat this process as long as you are in 4wd auto, it also cuts off the signal to the clutch pac at various turn angles of the front wheels.

In the similar manner when 4wd loc the front axle coupler is engaged and a voltage signal is sent to the clutch pac (supposedly it is a higher voltage) when the
computer decides it should also when slip is detected in the rear wheels. The rest of the function is the same as auto, so the only difference is a slightly more aggressive signal to the clutch pac when in loc as compared to auto.

This system will disengage the clutch every time the transmission is placed in park, even with the t-case still in 4wd.
So on a hill covered with wet slippery snow if you stop to get out of your vehicle when you place it in park you are in 2wd and
when you release the brakes the truck can and will slide in 2wd.

As far as I am concerned this is a fair weather transfer case that will work OK for most people for highway travel.
I know for a fact that my 2015 behaves almost the same in auto as it does in 4wd loc, you can drive it in figure 8's on pavement with no crow hopping or jerking from
the front axle.
In either mode if you try to back up a wet grassy hill your rear wheels will spin a bit before your front one start to work and this will occur every time you release the throttle if you are backing up to something on wet grass or a slippery surface every time you start and stop your rear wheels will spin and dig a bit before the front wheel do anything.
In moderate or good traction situations were 4wd drive is needed this system will work very good. As an example pulling a loaded trailer up a grade on a gravel road and turning onto a paved road you can use 4wd auto or loc and this system will do a good job and you can switch it to auto or 2 wd while accelerating on the paved road.

In 4wd lo loc this case functions the same as 4wd loc with a few minor computer differences and a considerable gearing difference.

The switch kit from Brandon W applies full voltage to the clutch untill you turn it off it makes this case work much much better in low traction situations.

Sorry for such a long post
Lou
Jeez Lou!!! Beat me to it!! Thank you lol
 

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Yeah, the way my dealership explained it was that 4X4 Auto is much like AWD.
Negative Ghostrider...AWD means all weels are driving the vehicle all the time. 4X4 Auto engages the front axle when slippage in traction is detected in the rear wheels.

4wd auto is a dangerous option, by the time the slip is detected you could end up in a ditch. I just use 4wd lock when needed.
It's faster than you can blink
 

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Negative Ghostrider...AWD means all weels are driving the vehicle all the time. 4X4 Auto engages the front axle when slippage in traction is detected in the rear wheels.


It's faster than you can blink
What is funny is that looking at the clutch force numbers while driving in 4wd lock, it behaves almost like an AWD vehicle. 1600 NM is max force so considered lockup and the truck spends little time actually locked up.

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