Always in AWD

Good afternoon,

With the truck parked and engine off, can you go under the truck and see if you can turn the front drive shaft?

Roy

It will not turn because the no vacuum engine condition engages the front IWE actuators which locks out motion I think, correct? I will double check and confirm when I get home tonight. Thanks for the quick response.

Let me know.

Roy

Cannot turn front drive shaft in either direction, but there is about 10-15 degrees rotational play.

Okay, the transfer case is locked in four wheel. When you command four wheel drive, does the hubs lock in?

Roy

Yes.

I thought that when the car is off there is no vacuum going to the IWE solenoid and therefore the actuators are engaged with the axles by default when the car is off correct? Not trying to argue but wouldn't the CV axles and thus the front driveshaft be in a locked position any time the vehicle is turned off or am I mistaken?

With the truck off, the front wheels should spin free of the front differentiate. Only when you command engagement do the hubs lock-in.

Do they lock in?

With the front wheels off the ground in the car in park with the emergency brake on when I spin the front wheels the axles differential and driveshaft all turn as a rotate either tire. Not until I turn the vehicle on does the vacuum solenoid retract the I WE actuators in the front wheels spin freely. When I rotate the shift selector to all wheel drive I feel nothing in the transfer case shift motor when I turn the shift selector to four high the motor actuates and 4 High Wheel Dr. locks in. When I turn it to four allow the shift motor actuates and the car locks into four-wheel-drive low. As I go backwards to four high the shift motor reengage is for high and when I go to all wheel drive the shift motor goes to the two high position and when I select back to too high the shift motor does nothing and I don’t hear any activity when I go from all wheel drive to two high. With the car into high and me backing down the driveway the front driveshaft differential and axles are rotating even though the front wheels are not engaged. I am wondering if the electron ask that tell the Transfer case to come out of all wheel drive is either not making the decision to do so or is doing so and that signal is not getting to the transfer case or it’s getting there and it’s not actuating to tell the transfer case to be into high versus all wheel drive.

Okay, Jim, this sounds like the normal operation of the four wheel drive system. I don't see any issue and have read many articles looking for this as an issue.

Don't think you have any kind of issue.

What makes you think there is an issue?

Roy

The 2003-2005 expedition reintroduced the 2high feature that sent all torque to the rear wheels only to take advantage of the gas mileage saving feature when the car was only in 2 high (I have read this in many places including my owners manual). I have 2 friends where I work with 2004's. When they are in 2H, none of there front drive mechanisms are engaged, and it can be seen that the cv axles are not turning when the car is slowing rolling in forward or reverse when the selector switch is in 2H(my car is always engaged). Not until A4WD is selected does their front drive gear engage and is available for 4WD should it be called upon to engage. Mine used to be AOK for years and not until the past 12 months have I noticed the additional vibration and "drag" on the rolling of the vehicle. My guess is that 4AWD is the default condition when the vehicle is not running. When I start it, the transfer case should receive the signal to disengage 4AWD and only transfer torque to the rear wheels if the selector switch is in 2WD.. If I knew the relay or relays that transmit the info I might be able to replace to resolve.

Let me look into this more and I will get back to you.

Roy

https://en.wikipedia.org/wiki/ControlTrac

This is one resource is found describing my vehicle. You'll find the sentence I referenced.

Two High mode was reintroduced on the redesigned second generation Expedition (U222) for the 2003 model year and featured a new full front axle disconnect system with vacuum operated front locking hubs that would disconnect the front axle, front differential, and front drive shaft when not needed for quieter, more fuel-efficient operation on pavement.[7] Ford claimed that the improved Two High mode could help increase fuel economy up to half-a-mile per gallon of gasoline.[7] In Two High mode, torque is routed to the rear drive wheels only, imitating rear-wheel drive.

Expedition also offers a new dedicated two-wheel-drive mode that completely disconnects the front axles, differential, and driveshaft when not needed for quieter, more fuel-efficient operation on pavement – saving up to a half-a-mile per gallon of gasoline.
I really do appreciate your help. Just trying to keep my main support, you, on the same page with me to resolve this issue.
Wish I had a list of relays that impact this system. I would change them all out and see!!!. I have used the owners manual basic stuff and checked all they suggested that had anything to do with 4WD to no avail. Gonna go back to the shop manual tonight and see if I can get lucky.

Jim

I have a friend who is a service manager at Ford. Waiting for him to call me back.

Roy

Hi Roy,

Any update.
Here are some additional thoughts if we work it backwards. I have been doing a lot of reading and can't find the answer to how this happens. Let us say nothing is wrong with a new 2004 Expedition and shift select from 2H to A4WD. What is the electronic pathway that occurs to get the front driveshaft to turn full time. If we knew this we could probably trace the potential path backwards and discover the culprit.

Another thought. If the transfer case shift motor has on three positions 4H, 4L, and 2H which is true. And it stays in the 2H position for 4AWD. Then the only thing that can trigger a change in the transfer case to engage the A4WD is through the one large white wire entering the transfer case that I believe activate a magnetic clutch (I think).

So if the default position of the car electronics and mechanics when off is A4WD. Which I am almost positive it is. Then I start the car. Shouldn't the white wire receive a signal to move something in the transfer case to throw all power to the rear wheels? Kinda like the IWE actuators. They are always engaged when the car is off. Then you start the car and the vacuum through the solenoid disengage them and holds them in that position until the solenoid engages them or you turn the car off.

Jim

I understand what you are saying.

I responded to you a while ago but it is not here. I have had issues where I respond to questions and it does not show. Have to talk to Max about that.

Anyway, what my friend told me was and he asked me this when you replaced the transfer case, was it the exact same part number? He asked because he was afraid you go an AWD case instead of the 4 wheel drive case.

The AWD will always turn the front shaft while the other will not.

Roy

Exact same Part. The other acted the exact same way as well. Oh, and I removed the white wire properly from the harness that feeds the clutch coil pack thing in the transfer case and it had zero effect. Interesting huh. I am leaning in the direction that the power is not getting to that wire to trigger activating the clutch which probably holds the transfer case in 2H mode but not sure what relay that could be bad is on that voltage pathway to that white wire. I will check again but have not seen a code thrown ever. Wonder if I jumper wire 12 volts to that coil clutch pack whatever and drive it down the driveway? What do you think? i'm still searching.

You can try that and see.

I will look at the diagrams again.

Roy

The yellow wire comes from the module in the truck. Diagram attached.

Roy

Any other ideas? We still haven’t solved the issue yet. Isn’t this fun?

You were going to check the yellow wire as per the last conversation?

Roy

Sorry for the slow response. Been doing a lot of reading on this topic, that is to say, as much as I can find. First of all the wire going to my transfer case housing is white not yellow. Interesting first observation but not sure what impact that has on our diagnosis. Second, the function of that clutch coil is to spin up that side of the transition to speed when shifting into 4WD while driving and my personal thought is that this really has no impact on the problem I'm having which I believe is a shift fork not disengaging from 4AWD back to 2WD. So as not to blow up the transfer case, now on the car, I did not apply voltage (worried that 12 volts direct from the battery may not be the correct voltage application of electrical power) to that clutch/coil pack in the transfer case.

Starting reading about earlier model of transfer cases and apparently 1999 (not sure of the scope of this style of transfer case set up) had a vacuum trigger to pull the shift fork back out of the 4AWD engaged position to the 2WD position. There is a large hose on top of the transfer case that I did not trace when I put the new (used) transfer case in. I assumed it was for moisture evaporation the way the IWE actuators have a small 1/8"ish version of hose that does this. Anyway, in the older models, the 4AWD to 2WD motion of the shift fork was vacuum triggered (I read that if there is a leak, the amount of vacuum applied would not overcome the force needed to pull the shift for out of the 4AWD position into the 2WD position) come to find out and thought I would trace this with some help on the top side to see if it was vacuum hose and evaluate that possible diagnosis. I reconfirmed, in my reading that the shift motor only have three positions of alignment, 2H/4AWD, (however it is labeled 2H) 4H and 4L.

Do you know if that lonely, single 3/8"ish port on top of the transfer case is evaporation or vacuum? We are running out of options. It is becoming a matter of pride and drive. I almost gave up last week.

Jim

Okay, Did you get this information?

Roy

Transfer Case-Automatic Four-Wheel Drive (A4WD)

Features and Operation
The Automatic Four-Wheel Drive (A4WD) transfer case uses an electronic shift 4x4 system that allows the operator to choose between four different operational modes. The operator can switch between 2WD, A4WD and 4WD HIGH modes at any speed. However, to engage or disengage LOW Range, the 4WD Control Module requires that the vehicle speed is less than 5 km/h (3 mph), the brake is applied, and the transmission is in NEUTRAL.
In A4WD, the 4WD Control Module varies the torque split between front and rear drivelines by controlling the transfer case clutch. Under most conditions, the 4WD Control Module activates the transfer case clutch at a minimum duty cycle (percentage of time the clutch is turned on) which allows for a slight speed difference between the front and rear drivelines which normally occurs when negotiating a corner on dry pavement. When the rear wheels are overpowered, the 4WD Control Module detects this slip condition, and the duty cycle to the transfer case clutch is increased until the speed difference between front and rear drivelines is reduced. In this manner, the 4WD Control Module can redirect engine torque to the front wheels when the rear wheels lose traction yet still allow operation in the A4WD mode on dry pavement.
When the ABS system is active, the 4WD Control Module will default to a minimum duty cycle for the transfer case clutch.
Feature Inputs:
^ Shift range selector switch.
^ ABS active input (battery voltage when ABS is active, grounded when inactive).
^ Contact plate position inputs A, B. C, D grounded when closed, open circuit when open.

Feature Outputs:
^ Solid state clutch relay (pulse width modulated signal: grounded when relay is on, battery potential when relay is off).

Shifting Between 2WD, A4WD and 4WD HIGH
The operator can switch between 2WD, A4WD and 4WD HIGH mode at any speed.

Shifting Into/Out of LOW RANGE
When shifting into or out of LOW RANGE, the 4WD control module requires that the vehicle speed is less than 5 km/in (3 mph), the brake is applied, and the transmission is in NEUTRAL.

I got it and have read this information a few times. Not sure what it is telling me? Should I be looking for an ABS active input fuse?

I read it as well. If it was the fuse, the ABS light would be on.

The hose is a vent line to atmosphere.

Roy

Here is my plan but not sure how it can help: I am going to go through all fuses and relays in the passenger kick panel fuse box on Sunday if time permits and test every one for continuity.

My concern is, that with only one wire going into the transfer case (powering the coil/clutch), and no vacuum lines, how can this be an electrical problem? The TCSM is in the correct 2H/4AWD position with only 4H and 4L options both of which would be wrong. I would give my left pinky to figure this out.

Here is the complete 4wd wiring diagrams with a guide to help you test the connection:

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Sorry, I have to the splined gear on the front axle side gets pulled into a neutral position when the white wire to the magnetic clutch coil receives power. That's the prob Bob. Now I have to find out why it is not getting power. Is there a simple relay you know about that I can locate and change? I don't think it is the TCCM because I tried three others and they didn't help. Any ideas?

I sent you the same diagram Ken sent you as well. There is no simple relay in the circuit.

Can you get a scan tool that can do bi-directional testing and see if you can command this thing into two wheel?

Roy

Not sure where I could get access to that tool.

It is a full blown scan tool, not a code reader.

It may be helpful to take it to a shop and ask them if they can check it for you.

Roy

Hope you’ll understand this short answer to this long problem to help someone else. Got new tires. Shop reset all TPMS’s! Problem gone and no longer in 4WD with the transfer case driving the front drive shaft, differential and axles. Wow, accidental but no one knew this for at least 3-4 years for having this issue.



Jim

Can I ask if the tires form front to rear were different sizes? Thanks for getting back to us after all this time :)

No. The tires were all the same size and brand both before and after the new ones were mounted and balanced. Weird, huh?

It must have been a balance issue?