Explorer 2002 4x4 Problem

[Lakey]

Hi everyone. Greetings from Australia.

I have a 2002 Explorer V8 XLT with an ongoing 4x4 problem. For no reason the 4x4 system engages and disengages every few seconds when under load. There is no light action, as would be normal if the system was engaging due to wheel slip.

The 4x4 system otherwise works fine and 4x4 High and Low can be selected manually. Interestingly you can manually fix the problem by selecting 4x4 high, which locks it in 4x4.

I first noticed this when I fitted slightly larger diameter tyres. 75,s rather than the stock 70’s.

Any suggestions????

 

[Charlie]

Welcome to the forum!

 

[E.B. Cornburner]

If the 4WD engages in the Auto mode, it then goes into an "intelligent" mode which will engage the 4WD automatically if the system senses enough throttle to create a spinout situation. It's trying to think ahead of a possible problem.

If you push the 4x4 HIGH button and then back to 4x4 AUTO while coasting, it resets the system.

Larger than stock tires may aggrivate an already over-sensitive auto 4x4 system.

 

[manaen]

Have you check all of your ABS sensors to make sure they are ok?

the auto system locks in based on the readings from those sensors (one on each front wheel, and one in the rear axle). If the computer senses that the rear wheels are spinning faster than the front ones it will try to engage the 4x4.

EB may be onto something, have you rotated your tires lately? if your back tires are wearing a lot more than your front ones, the diameter may be so far off that the rear wheels are spinning faster. Larger tires will accent this problem

For example on a 31" tire 1/4" of tread wear difference will make about 1 1/4" difference in roll distance on every revolution. Or to put it into plan terms when the front is rolling at 65mph the back is going about 66mph I'm not sure how sensitive the computer is but maybe if there is enough difference from front to back this could cause this problem. But that is all just theory of course

I could see how an more worn and under inflated tire could cause problems with the auto system. Either way you need to figure it out because the constant wear on the clutches will wear out your TC

 

[Lakey]

4x4 Problem

Hi guys. Thanks for your input.

I have been playing around today with tyre pressures. Putting two and two together, I realised that when I left for holidays last week towing a boat that I had increased the rear tyre pressure 7psi more than the front. It was on this trip that I noticed that the problem was much worse.

I have now dropped all four tyres to equal pressures and have all but eliminated the problem.

The whole tyre size and pressure theory makes sense to me and I think I will keep playing with this rather than replace the 4x4 module which has already been done once before.

 

[manaen]

Hopefully that is it, but I just don't know how sensitive the 4wd module is to speed differential between the front and back, I'll check the ford CD and see if they have the specs on that.

 

[capewelr]

4auto operation

I learned to my cost that the controltrac system in 4auto is very sensitive. I had a blow out on one of my '99 Explorer 4x4 Eddie Bauer tyres. So I replaced it and soon after noticed a rumble under the floor. Took the car for a service and Ford diagnosed the rumble as mix & match tyres causing the 4x4 system to engage permanently. They said this strains the diff, trying to make up the difference in tyre rotations in the dry all the time.

I didn't believe them, so researched the internet and spoke to many engineers. Anyway, end result of my research is that if any tyre is as much as 1/4inch different in diameter from any other then the ABS sensors will pick it up and the 4auto mode will engage the diff. Thinking about this another way, only 1/8inch difference in tread depth (or under/over inflation) will kick the system into 4x4. I had to buy 3 more new tyres in the end, and wonder of wonders the rumble disappeared straight away. This is also why Ford recommends to rotate tyres every 5000 miles!

 

[manaen]

This is all a great reason to install the infamous "Brown Wire Mod"

 

[wickedme45]

Im also experiencing a similar problem when there is snow on the ground i go to take off from a light and the 4 wheel kicks in and out but if i floor it it just stays locked in and if its dry it dont do it at all when i just put it in 4 wheel its fine i dunno what the problem is

 

[GregV8]

I know this won't be any help but I used to own a Trailblazer which had the very same problem. No technician was able to figure out what was wrong not even some "expert" sent in by GM (it was a warranty problem). They checked everything, including ABS sensors, tires, replaced the 4wd control unit. This expert actually tried to convince me it was normal. At least that truck had a 2HI mode as well.

 

[manaen]

At least that truck had a 2HI mode as well.

That's what the brown wire mod will give you is a true 2hi mode.