Auto 4x4 engaging in rain?

[E.B. Cornburner]

This is wierd...Last couple days it's been raining quite profusely here, and I noticed something odd; when I'm driving on wet roads and get on the throttle to either speed up or pass a car, etc. I can feel additional driveline vibration from the front end which indicates to me that torque is being applied to the front axle. Lift off the throttle, and there's a noticeable "bump" as the trasfer case disengages. I wouldn't think the small amount of throttle input I was giving it would be enough to break the rear tires loose enough to cause the 4WD to engage. It also seems to stay engaged too...After lifting off the throttle, and lightly getting back on it still tells me it's in 4WD. Are these designed to do this?

On dry roads, it doesn't do this at all, no matter how hard you get on it.

Are these systems just that sensitive, or should I be looking for a problem?

I've never experienced any others that do this, but none of them had AdvanceTrac either. Not sure if that makes a difference or not...The "AdvTrac Active" message was never displayed on the message center.

 

[E.B. Cornburner]

Just to add more to this...

It did it again yesterday, but this time, I pressed the "4x4 High" button, then went back to "4x4 Auto", and it released and went back to 2WD operation.

It seems that if it goes into 4WD from the Auto mode once, it tends to stay engaged even after there's no loss of traction. Once the vehicle is shut off and restarted, it seems to reset itself though.

I'm just not real familiar with how this system operates, and if this is something that it's designed to do.

 

[BWilliams]

Are you sure that it's remaining in 4x4? In my '05, I can feel and hear it engage if I get slip, but I sometimes don't feel it go back to 2 wheels.

EDIT: I know that it falls back to 2, though, because the drivetrain sounds different on pavement then 4.

 

[E.B. Cornburner]

After it engages the front axle due to rear wheels slipping, and I get on the throttle, it definitely feels like it's still in 4WD. Lift off the throttle, and you don't feel it though.

I talked to a very knowledgeable person at the Ford dealership today, and she told me that it's a common thing that they get asked about these vehicles. She also said there's no real answer from Ford as to how long the system stays engaged after no wheelspin is detected.

I guess I feel a little better knowing I'm not alone, and I'm more or less considering it normal operation.

It'd just be nice to have a better explaination as to how the whole system works when it's in the Auto mode.

 

[Critter92X]

I've noticed that heavy rain tends to "confuse" (for lack of a better word) my auto 4x4 also.In all other conditions it seems to work fine.I don't worry about it too much although I have wondered just how much of the time it stays locked in when it's really wet pavement.

 

[kert0307]

I know the auto 4x4 in my 2000 is different, but it sometimes does something similar.... My theorey is that the auto computer is more active the more it is used. I say this because I have done the brown wire mode and have the light on the switch. When 4x4 is completely enguaged it it bright, and if the auto is slightly kicked in it is dull, and everyhting in between.

When it's snowing out, or very muddy, if I keep it in auto, it will atcually completely stay in 4x4 if I spin a lot, even after I stop spinning. It also locks into 4x4 faster too rather than slowly easing into it like normal.

So, I think there is a sort of memory in the computer so it locks up easier when it is more slippery out...

 

[ntrpriz]

It is a very sensitive system. Mine will lock in backing up with the wheel turned at full lock. I think thats a little too sensitive, but it seems to work fine and nothing has ever broken (knock on wood).

 

[DavidS]

My '02 started doing the same thing thing after replacing the 4WD module when the 4WD light started blinking. They suggested replacing the tranny fluid in the front transfer unit as this seems to be common in '02 models. It didn't help and now it does it when dry on any sort of a grade in high gear as well. They now say that either the wheel speed sensors are bad or the clutch pack in the front transfer unit and they won't cover it under warranty even though the problem was reported while the warranty was in effect. A sucky problem at best.

 

[Curtis]

It is a very sensitive system. Mine will lock in backing up with the wheel turned at full lock. I think thats a little too sensitive, but it seems to work fine and nothing has ever broken (knock on wood).

Steve,
I feel the same thing in my 04 just about every time I back into my driveway.. Its a PITA....I'm still researching for a "Brown Wire Mod" for our 3rd gens...For example, my dad has his 4x4CM disconnected and has full time 2WD now. His 4x4 lights still flash.

We did this because of flashing 4x4 lights in the first place until I get the new module to him. His gas mileage has gone up considerable. On the last highway trip with module disconnected he got just over 420 miles to the tank! And its a 4.6 too.

 

[E.B. Cornburner]

In the interest of adding more information as to how this new Auto 4x4 system works, I've got it pretty much figured out now.

It's considered "intelligent" 4-wheel drive. If the rear wheel speed sensors detect slippage enough to engage the transfer case, the system remains on kind of a "standby" mode in case more traction is needed. You can feel this if you for example spin the tires in gravel, then go out onto a paved road. The system will engage in the gravel giving torque to the front, but then after you're on a perfect road, if you go beyond a pre-determined amount of throttle, the transfer case will engage again. The system I believe is designed to help prevent wheelspin before it happens. Since it saw wheelspin once, it thinks that there still may be a low-traction situation, and tries to prevent further wheelspin by engaging the front end when it feels like there may be enough power on the rear to cause a possible wheelspin. It tends to be more sensitive at higher speeds too.

Eventually, it will finally disengage completely, but it takes forever to do so. To the tune of 10 miles or more of driving with no wheelspin detected. You can reset it manually by quickly shifting from Auto 4x4 to 4x4 High and back again, like I discovered a while back when I first posted this thread. The system also resets when the vehicle is shut off.

Since nobody around this area really seemed to know much about how it worked, I took it upon myself to find out everything I could about it, and so far, what I've posted is my conclusion based on what I've learned about them.

 

[Pinshooter13]

So, since I wanted my wife to drive a 4 wheel drive vehicle that was smarter than her, I bought the right one?

 

[E.B. Cornburner]

I've met some women that had a hard time figuring out a headlight switch, so form your own conclusion.:

 

[02whiteXLT]

mine does the same thing, when im making a turn on a wet road it ussually engages but most of the time its becuae one of the tires spins a lil, what is really anoying is the auot 4wd engages it engages for like 1sec then off then off and if you going up a hill it makes a jerking feel, they need a better design have it engage for 1min if no sliping detected it should go back to 2wd