4 Wheel Drive/SUVs/four wheel drive

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Expert: - 2/3/2012


Question
the four wheel drive on my 2002 explorer will not disengage but it will shift from four low to four high?

Answer
Aaron,
There are numerous components that can cause this problem.  The one that usually is the prime suspect, is the MSS (mode selector switch.)  It may not be making a good connection in the normal operating position, which could be due to a bad switch,  or faulty wiring.

It could be a 4wd control module also.

As there are several things related to this problem, I would purchase a repair manual for the Explorer as it will have a trouble shooting section and diagrams of components and wiring for testing.

If you can't figure it out yourself, you may have to go to a reputable shop and have it diagnosed with a scanner.

The following is a list of related components that need to be checked.

Four-Wheel Drive Systems - Automatic Four Wheel Drive (A4WD)
The automatic four-wheel drive (A4WD) system is an electronic shift 4X4 system that utilizes the following components:

   * transfer case
   * four-wheel drive (4WD) control module
   * mode select switch (MSS)
   * gearmotor encoder assembly
   * electric shift motor (part of gearmotor encoder assembly)
   * shift motor sense plate (part of gearmotor encoder assembly)

Early Build / Late Build Definition
Early Build - Vehicles Built Before 03/2002
Late Build - Vehicles Built After 03/2002

Carl

4 Wheel Drive/SUVs

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Carl Brandt

Expertise

Will discuss suspensions, lifts, lockers along with tire suggestions. Trail ratings and possible requirements needed for specific type of trails. Safety equipment and what you should carry with you. Certified off-road instructor. I am not a mechanic, and 4-Wheeling is a hobby, so if I can't answer a technical question it is due to my mechanical knowledge being related to vehicles that I have owned, or have worked on. I do not have manuals on all vehicles.

Experience

40 plus years of 4 wheeling in a variety of vehicles. At the present time, my major off-road rig is a 94 Jeep Wrangler with a spring over and a 1 1/2" suspension lift. This gives me a total lift of 7" or so. I have lockers front and rear. I have removed the track bars, and sway bar for maximum articulation. I am running a stock 2.5 ltr 4 cylinder with a Jacobs ignition along with a cold air high flow filter. It has 4.56:1 gears with a Dodge NV4500 transmission along with a 3.8:1 Atlas II transfer case. This gives me a final ratio of 105:1 in low gear/low range. Other vehicles I own, are a 96 Ford F-250 with a 6" lift, posi rear end, 36" Hummer tires, 5 speed with a fuel injected 460 ci engine, an 87 Samurai with an 8" lift, Ford 9" rear end with a spool, Chevy Dana 44 front end with an electric locker, 5.88 gears, 16% reduction in high range and a 6.5:1 low range with 35" Baja Claws, and a stock 2003 Grand Cherokee Overland. Trails I have run are the Rubicon (10 times), Dusey Ershim, Fordyce Creek trail, McGrew trail, several trails in Moab, Utah along with local monthly runs.

Organizations
Lost Coast 4x4's Cal 4-Wheel Corva UFWDA Blue Ribbon Coalition

Education/Credentials
Certified off-road instructor - Certificates in engineering/electronics

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