Understanding 4x4 Operation NonOperation 2002 XLT

[splib]

I am familiar with conventional 4x4 manual transmission and transfer case operation. Easy, clutch, stick, low or high range. Manual hubs. Easy. My newish to me vehicle is another matter. I need to understand what and why before I go any further or $$$. Purchased with 144,000 miles. The 4x4 worked. 3 Positions Auto High Low. In Low the front end would bind when turning in a paved parking lot, with the Low light on just as it should. Somewhere along some miles, the system quit. The indicator lights do not light, and any apparent 4x4 function is gone. The one time I needed, really needed my front axle, no dice. Stopped on a steep uphill with both rear spinning making clouds of dust, no, zero front traction. No buttons able to do anything.

So.... if the system defaults to 4x4 with 75% rear, and 25% front, why doesn't it bind at low speed on paved surface ?

And, what specifically would entirely disconnect the front axle ? Is this a function of the Traction control module, AKA 4x4 computer found behind the glove box ?

If the answer is a cpu, are the rebuilt ones a safe purchase and does the Vehicle CPU have to be integrated by a dealer or other effort ?

Thanks !!

 

[974X4BLACKSPORT]

First thing you want to check is the shift motor on the T-case. Instead of a shift lever and rod to engage the T-case like in older 4x4's, the newer cars use an electric motor on the T-case to move the internal selectors for gear engagement, it is very common for this e- shift motor to become in-operable. I know on the older ones (1995-2001) the shift motor can be partially dissembled, cleaned, and reassembled to make operative.

 

[Mbrooks420]

You’ve got an issue that isn’t your shift motor. The shift motor does nothing between Auto and high.

You’re transfer case doesn’t always power the front axle, it only does when it detects slippage between the front and rear axle.

You possibly have a 4wd module issue. Do you have an ABS light on?

 

[splib]

You’re transfer case doesn’t always power the front axle, it only does when it detects slippage between the front and rear axle. - My "road test" demonstrated that front axle was not engaging at all, with both rear tires kicking out clouds of soil. Maybe this helps diagnose.

You possibly have a 4wd module issue. Do you have an ABS light on? - No ABS light on, never seen it while driving. Didn't notice it during my near stuck 25 miles away from nowhere event at 7,500 ft. I checked just now, the ABS comes on when you turn the ignition key, along with the Airbag, parking brake lights etc.

I had the Tranny rebuilt at a reputable shop since the 4x4 issue manifested. My guy said the front axle non-op is not a mechanical issue as far as he could tell. As I had asked, he looked for problems and pulled codes. He said it's probably the 4x4 module, but to take it to Ford for more sophisticated code diagnosis. It sounds like I can get a Doorman rebuilt module for less than Ford will even charge to plug in the scan tool. Is a rebuilt module at $140.00 a gamble relative to the OEM parts ? - thanks

 

[IPcamper]

Your explorer has a Borg Warner 4411 transfer case. It has an electric shift motor to engage the High/Low range and an electric clutch to engage the front drive shaft.
here is an article that gives some info. http://tcase.rsgear.com/articles/2008_05.pdf

You should check the fuses to see if the electric clutch is getting power, if so, then clutch coil may have failed.

Also, the Ford manual states that the 4x4 auto mode should be used for normal driving on the road. The 4x4 high and 4x4 low should only be used on snow, ice, or off road conditions. prolong driving on hard payment in these modes can damage the clutch assembly.

 

[IPcamper]

You might want to take a look at this post from a while back. 2002 4x4 issues

 

[kydirtscooter]

The 4x4 Control module can have internal problems, but you can find on ebay used for less than $100. They do need initial programming but if you buy a tested used one then it has the program already.

I would not buy anything dorman, they make junk. I wouldn't trust them to reman anything either.

 

[imp]

@splib

In 4X4 AUTO, the front wheels receive NO POWER unless a difference is detected between front and rear wheels, not between fronts, or rears. Normal driving on pavement never engages the front wheels, except possibly in the case of a violent skid, very remote.

4X4 HIGH engages the front wheels ALL THE TIME. It should never be used on any paved surface.

4X4 LOW engages the front wheels ALL THE TIME, but offers a lower gear ratio through the transfer case.

The T-case shift motor has NOTHING to do with 4X4 AUTO or 4X4 HIGH. The motor only shifts the transfer case into and out of it's low gear.

All power sent to the front wheels is delivered through the use of a magnetic clutch which is turned on by the PCM in 4X4 AUTO, and by the driver in 4X4 HIGH and 4X4 LOW. This clutch is NOT DESIGNED to slip, it's either engaged, or not.

Does this help? imp

 

[splib]

Thanks all for input. Bottom line may be the dealer to hit this on the first swing. Or; There is a shift motor replacement switch that bolts onto the back of the case. This allows manual, reach from under the car selection and operation. This may in theory obviate the need for the electronics entirely, right ?

As stated Very well versed in manual 4x4 operation and driving but not this electronic stuff - thanks all !!

 

[Mbrooks420]

There is no way to manually switch into 4wd as stated above. The most you could do is switch to low, but without the electromagnetic clutch functioning, all you’d end up with is 2wd low.

Don’t take this to a dealer unless you like throwing money right in the garbage. Take it to a well reviewed transmission or driveline shop.

 

[splib]

There is no way to manually switch into 4wd as stated above. The most you could do is switch to low, but without the electromagnetic clutch functioning, all you’d end up with is 2wd low.

Don’t take this to a dealer unless you like throwing money right in the garbage. Take it to a well reviewed transmission or driveline shop.

Message received and understood. Have to find the shop. Thanks.

The rest of it !! The CONNECTION between the Tcase and the front wheels is, working back from the rubber: Hubs, some type of birfield or u-joint, front half shaft or axle, front diff, output shaft, joint, driveshaft, Tcase clutch, Tcase gears. If I understand this correctly (?) the entire front drivetrain is rotating all the time, except it is disconnected at the Tcase. Creating wear, friction and heat and drag. If manual hubs were installed, ( if feasible) would this operate any more efficiently or not ? ?? Doesn't help that it all sits so low it's difficult to simply slide under and figure it out. I truly miss my Isuzu truck. But, this baby has a ton of room and rides well.

 

[imp]

Message received and understood. Have to find the shop. Thanks.

The rest of it !! The CONNECTION between the Tcase and the front wheels is, working back from the rubber: Hubs, some type of birfield or u-joint, front half shaft or axle, front diff, output shaft, joint, driveshaft, Tcase clutch, Tcase gears. If I understand this correctly (?) the entire front drivetrain is rotating all the time, except it is disconnected at the Tcase. Creating wear, friction and heat and drag. If manual hubs were installed, ( if feasible) would this operate any more efficiently or not ? ?? Doesn't help that it all sits so low it's difficult to simply slide under and figure it out. I truly miss my Isuzu truck. But, this baby has a ton of room and rides well.

@splib
Yes, the entire front driveline spins all the time. This is to allow the option of instantly engaging the 4X4 AUTO function. If manual hubs were installed, there would be total loss of the 4X4 AUTO option. Yes, slightly more frictional losses with constant driveline rotation. How much? Hard to say, really. But, these spinning parts, especially U-joints and CV, if so equipped on the front driveshaft, last very long because the driveshaft operating angle is fixed, not changing all the time as with a solid axle. imp

 

[Mbrooks420]

The entire truck is such a pig I wouldn’t worry about the tiny gain from not spinning the axles and diff. Plus you have the inconvenience of having to get out to lock and unlock the hubs.

 

[splib]

Thanks. This explains the whole mess ! ControlTrac - Wikipedia

 

[Mbrooks420]

That article isn’t entirely correct. The axle is locked to the hubs, always, no matter what, unless you have an early second gen with the vacuum disconnect.

Also, it’s a electromagnetic clutch, not s locking “differential” that ties the front and rear axles together.

 

[MrPulldown]

Hit the 4hi button. Check 12+v power at the brown wire.

Most new 4x4 don't have a disconect at the front hubs. There have been people who have modded their front hubs and added a manual locking front hubs. Generally they get 1 to 2 mpg out of the effort.

I recall my FIL leaving his front hubs of his K5 Blazer locked all the time in the winter. That why he could "shift on the fly". Actually I think he need to stop the truck to shift into 4wd, but at least he didn't have to get out at the inclined intersection when it was icy out. Ahead of his time.

 

[Mbrooks420]

Most people who have real winter leave their hubs locked all winter...

 

[splib]

Foooook. Seriously. Have any of you tried to access the 4x4 module behind the glove box ? I gave up after an hour.
Might come back at it with a 12-pack of Hamms and a cut off wheel or a torch !!

Re: hubs - uh I ran the Rubicon Trail both ways several times in my previous life in an Isuzu etc.

 

[MrPulldown]

Test the brown wire. If you have voltage with it in 4hi then your modal is fine and the t-case is the one that is FOOOOKED.

Hammmms. Where you get that stuff in CA. Assume you are close to the Rubi. i am about 15 miles away from the north end as I sit and type.

 

[splib]

Hit the 4hi button. Check 12+v power at the brown wire.

.

Have to get my oHm meter from storage. To access the rear of the dash 4x4 control switches . .. . pop them out ??. what 4 - 5 wires ? If you are inclined and do this routinely, it's easy. To us it's out there. Give it a shot tomorrow. Thanks !! FWIW I carefully watched the dash on ignition and the yellow 4x4 Low light comes on briefly along with the brake, ABS and Airbag.