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4x4Auto Question


November 28, 2011
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Year, Model & Trim Level
2006 Explorer V8 AWD
This is a long write up so thanks in advance and any advise is appreciated. All the symptoms started right after I replaced my plugs and COPs. Mine is a 2006 XLT V8 with just shy of 100k on the odo. All new tires all around and properly inflated.

Before the plugs and COPs, my 4x4Auto mode pretty much remained in 2wd mode during regular dry pavement driving. When I switch to 4x4Hi, I could really feel and hear the front engage. The engine sounded much louder and turning was more strained. It also wouldn't engage into 4x4Lo. I had been meaning to bring it to the dealer but never got around to it. This is how it was for about 2 years since purchase.

After my recent plugs and COPs replacement, the engine feels much more powerful, no more misfires and much better fuel economy. But about a week afterwards, during regular dry pavement city driving, I started feeling the front engage while in 4x4Auto, no dash lights. There was louder engine noise and what seemed like a bigger drain on the engine. Steering felt normal, not weighty and seemed to turn ok, not like it would if in 4x4Hi. Highway driving is not any different than before, but getting up to speed is much louder at times. There are no lights on the dash. And now, miraculously, 4x4Lo engages as it should. 4x4Hi and 4x4Lo dash lights come on appropriately.

It seems very random when the truck decides to engage 4x4 mode while in Auto, but it is noticeable. Usually during acceleration from a stop light and it takes forever to disengage, if ever. Once truck is turned off and restarted, we are back in 2wd mode. And sometimes I can drive for miles without it ever engaging again.

I started to read up on 4x4Auto randomly engaging and there seems to be lots of different information. Some say it isn't normal and to check wheel sensors, the TC, the electronic 4x4 module, etc.

I also read some posts that say it is normal for the explorer to engage 4x4 mode in Auto and that the TC will send power to the front most of the time even on dry and during acceleration, that it is a feature of the AdvanceTrac system. And there are a lot of mods to deactivate this; I've read about the brown wire mod on the older models and the fuse pull on my gen. Also read about the wire disconnect from the 4x4 controller module all to try and keep the truck in 2wd mode.

So I'm wondering is the current behavior for the truck normal, the randomness of the front engaging? I'm also confused as to why my 4x4Lo is now working. I don't know if the plugs and COPs had anything to do with it or if it is purely coincidental.

FYI, I did remove the fuse for a bit and drove around and that is what I am used to, regular 2wd mode without 4x4 mode kicking in at all.

Any insight is welcomed.

The Auto4x4 system in Explorers is the same as the AWD system in the Mountaineers. In both trucks, if a V6, it's a type of system that is always sending some torque to the front wheels, then adds more if needed. Not so for our V8 systems, which are supposed to be 100% rears unless slip is detected. You should not have any front engagement when cruising or normal acceleration on dry pavement. Stop on the gas? Yeah, it will momentarily use the front wheels, and might even engage the traction control if that's not enough to stop rear wheel spin.

It sounds like you are hesitant to take it in for a check. Why? This is not normal behavior, and disabling the 4x4 is not the answer. You very well may have a wheelspeed sensor that is misbehaving enough to trick the 4x4 system, but not enough to throw an ABS light. Or maybe something is wrong in the center differential, that is causing it to engage.

Keep in mind, when you hit the 4x4HI button, this locks the center diff into 50/50 torque split. This is the same as me going into my menu system and engaging "4x4 LOCK" on my Mounty. In this situation, like you said, you will feel it bucking when you turn on dry pavement. You probably know not to do this regularly, as you could do damage.
But you are feeling it engage when in 4x4Auto, yet you don't feel it bucking when turning on dry pavement. This tells me it's not really completely locked. Something is preventing the center diff from completely disengaging. It's sending torque to the front wheels, but its not locked so hard that it won't let you turn. It's actually working like a poor-mans limited slip!

I would take it to a dealer, and tell them everything you are experiencing. If you haven't already done so, it's probably time for getting all 3 axles serviced anyway. But I suspect issues with the center diff, specifically an inability to keep it completely disengaged.

I just had the same thing happen to my 2006 Limited 4.6, but it turned out to be the clutch fan engaging. I had the radiator replaced but its leaking again after a month.

So I drove around for several weeks with the 2 4x4 fuses pulled. The wrench was showing on the dash display but all was working well. Then one day, the car felt like it was running on 4 cylinders. I parked it in the garage and replaced fuses and disconnected the battery for a few days and used my other car. I connected it all up and have put on about 1000 miles with no hiccups. 4x4 auto now works wgen it's supposed to, as does the Hi/Lo settings. So weird. I'll end up bringing it to the dealer if the problem pops up again.