4wd "Auto" Engagement Problem

[gabateman]

'02 Explorer w/ 4.6 V8

Hey guys...have been trying to diagnose a problem with my 4wd AUTO function for the last couple months and with the heavy snow this week, the urgency to find a fix has increased.

Problem is an intermittent engagement of the front axle under power, feels like a mechanical on/off every couple of seconds. On the gas, you can feel a 'skip' in the engagement, but the front axle is definitely engaging. Very noticeable on the ice this morning!

If I put it in 4wd HIGH, the problem goes away 100%. If I disconnect the two modules under the passenger-side dash, problem goes away. There are no warning lights or issues shifting between HIGH/LOW.

So over the summer / fall, I just ran with the modules disconnected, but would like to find a permanent fix.

Any ideas or fixes applied for this issue would certainly be appreciated!

 

[mark2016]

'02 Explorer w/ 4.6 V8 Hey guys...have been trying to diagnose a problem with my 4wd AUTO function for the last couple months and with the heavy snow this week, the urgency to find a fix has increased. Problem is an intermittent engagement of the front axle under power, feels like a mechanical on/off every couple of seconds. On the gas, you can feel a 'skip' in the engagement, but the front axle is definitely engaging. If I put it in 4wd HIGH, the problem goes away 100%. If I disconnect the two modules under the passenger-side dash, problem goes away. There are no warning lights or issues shifting between HIGH/LOW. So over the summer / fall, I just ran with the modules disconnected, but would like to find a permanent fix. Any ideas or fixes applied for this issue would certainly be appreciated!

Mines an '01 but I think the system is the same, and what I feel in the Auto setting sounds similar to what you're describing and mine is working fine. Have you had it tested, wheels off the ground? Or are you referring to the spinning of front and back wheels simultaneously which is possible in deep snow.

 

[gabateman]

Yes...I have put it on a lift and could not duplicate the problem. You can only feel it while under load / hard on the gas.

 

[cjben]

I think it's normal...and I hate it on our 04,but I don't drive it much so I haven't went through the trouble of disabling it.

 

[gabateman]

Thanks for the reply...does not feel "normal". On dry pavement, it definitely feels like the front axle is intermittently disengaging under power. I understand there is like a 5% load on the front axle in AUTO mode, this feels like maybe an electrical issue causing the transfer case to momentarily disengage.

 

[drdoom]

How are your tires? Are they a matching set with equal wear?

 

[gabateman]

Tires are new within 10k miles...Goodyear Fortera's.

 

[dla]

The system does disengage when the front and rear wheels are going the same speed - that's how it is supposed to work. The purpose of this system is to prevent you from spinning and sliding the rear end around when taking off from a traffic light, etc.

I have a lot of experience driving rear-wheel drive vehicles on slippery roads, and I'm used to managing rear wheel slip. I personally don't like the Ford Control-Trac system cutting in and engaging the front wheels - feels a little squirrely to me. So when driving on snow/ice I leave it in 4wd-high.

 

[dla]

Thanks for the reply...does not feel "normal". On dry pavement, it definitely feels like the front axle is intermittently disengaging under power. I understand there is like a 5% load on the front axle in AUTO mode, this feels like maybe an electrical issue causing the transfer case to momentarily disengage.

You shouldn't feel it on dry pavement. The only time you should notice it is when you spin the rear tire. The system will react faster than the LSD rear end.

 

[gabateman]

Thanks for the explanation...happens as well on dry pavement in a straight-line acceleration without any wheel spin. Hard to describe, but it almost sounds like a mechanical 'knocking' sound and / or hesitation.

 

[dla]

Thanks for the explanation...happens as well on dry pavement in a straight-line acceleration without any wheel spin. Hard to describe, but it almost sounds like a mechanical 'knocking' sound and / or hesitation.

Definitely something wrong then. Since you said you have good tires, (the system can't tolerate a small difference in tire diameter), I would focus on wheel speed sensors first. Everything OK with the ABS system?

By the way, are you sure you're not feeling the limited slip unlocking in the rear? So if there is no friction modifier in the rear differential fluid, you might get the rear end to "lock" when spinning and then "unlock" rather abruptly some time later. Just thought I'd ask.

 

[gabateman]

DLA...thanks for your input.

ABS system is working good, no codes / no lights, so I somewhat eliminated wheel speed sensors as well.

I noticed the problem over the Summer after I bought it, then unplugged the TC modules and the problem went away. In the meantime, I did the transfer case fluid and the rear diff service, using the Ford friction modifier.

Definitely not the rear limited slip...definitely in the front.

 

[05XLimited]

Since you have eliminated the ABS Rings within the wheels and the tires are the same size, the 4x4 control module on the 02-03 has given people many headaches. Most of the time it will not engage, but I think there was somebody on here who had a similar issue. They replaced the module and it worked again.