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4 Wheel Drive/SUVs/1999 GMC JIMMY 4WD NOT WORKING CORRECTLY

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Expert: - 9/18/2007


Question
i HAVE A 1999 GMC JIMMY THAT THE 4WD ISN'T WORKING CORRECTLY IN. WHEN I TURN THE VIHICLE ON ALL THE BUTTONS ON THE PUSH BUTTON 4WD WILL LIGHT UP AND GO STAIGHT TO THE AUTO 4WD AND IN ORDER TO GET IT BACK INTO 2WD I HAVE TO UNHOOK THE CONTROL MODULE UNDER THE GLOVE BOX ON THE PASSENGER SIDE.  DO YOU HAVE ANY SUGGESTIONS TO WHAT COULD BE WRONG WITH IT?

Answer
Andrea,
It sounds like you have a short in the control module, or a shorted switch.  This may not be too hard to trouble shoot yourself, if you purchase a repair manual.  They can be bought at most auto parts stores for around $20, and have a full trouble shooting section.  You can look this up, and see what it takes to test the control module and associated components.
Other than that, you may need to take it to a reputable transmission shop, preferably one that specializes in 4-wheel drive vehicles.

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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