Wife's 98 GMC Jimmy O.T.

Butch (PA) · Feb 3, 2011

Guys,
My wife's car the GMC Jimmy 4 wheel drive that has the buttons to push from 2 to 4 high and 4 low.
The problem is that when you push the other buttons other than the two wheel drive, the 4 wheel will not kick in.

Sometimes the 4 wheel low button will stay on and the car "acts" like it is in 4 wheel, but isn't.

Finally have to go into neutral to get it back into 2 wheel.

What's the solution? I need help, no money for garage, if you know what I mean.

Bryan inIowa · Feb 3, 2011

What year is it ,,makes big difference . Last one I had in shop had couple bad vac lines and a bad vac solenoid to the front axle acuator , solenoid is on cowel right by wiper motor . Vac line feeds off drives side of intake in the middle , goes up to a TEE fitting by fender . Lots of problems with these but need more info .

Anonymous-0 · Feb 3, 2011

I had a 93 s-10, that had 4wd problems, don't know if yours is the same trouble, or not, but chebby very wisely, from an injuneering viewpoint, put the vacuum actuator, for the 4wd, under the battery, where any acid or corrosion, could eat up the diaphragm! As I said, don't know if that's your problem, or even if your vehicle has the same configuration.

buickanddeere · Feb 3, 2011

The system shifts better with high intake manifold vacuum which occurs during de-acceleration.

ted regentin · Feb 3, 2011

This is tough to diagnose over the internet. In addition to vacuum lines and actuators, there is a shift motor and control module for the transfer case. The first thing should be to check with a scan tool and see if there are codes. Some years of this body style can be difficult to pull codes, I am sorry but I work on too many years to remember exactly which years. As someone else said, the vacuum actuator for the front axle under the battery is a common issue. Also, check for melted vacuum lines going to the vacuum switch on the t case.

JDseller · Feb 3, 2011

You need to look and see if the vacuum is shifting the transfer case first. IF it is not then check all of the vacuum lines, they crack with age. If it is shifting then your front differential shifter is not working. Again check the lines first. Also these vacuum front shifter are notorious for sucking moisture into them and then freezing up and not shifting. There are several companies that make a manual cable shifter to replace the vacuum one.

I hate these type of 4wd shifters. Give me a good set of lock out hubs and a floor shifter any day. Another thing these do is if you stop in 4wd and turn the engine off they shift back into 2wd so when you go to take off again they are in 2wd for a bit until the front differential gears lock in again. My boy"s newer pickup is a dud doing feeding chores because of that. When it is muddy that little bit of spin to lock everything back up is enough to get you stuck.

Butch (PA) · Feb 3, 2011

it's a 98 Jimmy

Ron Anderson · Feb 3, 2011

I have a 95 S-10 that did the same thing. it takes a while to check everything but it ended up being the vac actuator under the battery. Replaced that and works like new. The old one lasted to 270,000 miles so can't complain.

JayinNY · Feb 3, 2011

Check the vac lines, mine are cracked on my f250 and wont go into 4wd either, I have to get out and lock the hubs. I hate that setup, why couldent they just stay with the floor shifter, I never have a problem with them in my other trucks.

VADAVE · Feb 3, 2011

Check on top of the front axle beside the pumpkin there might be a connector there that has disconnected. I wound up wire tieing mine together.

bradk · Feb 3, 2011

With key on,you should hear the encoder motor(t.case motor)change gears when you push buttons from 2 high to 4 high and visa-versa.There are position sensors inside the encoder motor that fail and shut the system down.Unhooking the battery temporarily resets the position and motor will work until an error is seen again.

Start there.

RayP(MI) · Feb 3, 2011

Also take off the plug on the top of the transfer case, clean, and spray down with contact cleaner, or at least WD-40 - both sides, and put back together, make sure connection is good. Mine was giving me problems, and I had to replace dash switch - about $25.

RayP(MI) · Feb 3, 2011

doesn't that one have electrical servos to engage 4wd? My blazers 2000, 2002, 2004, all have all electric. All connections are suspect. There's a relay board behind glovebox that you should hear clicking to engage/disengage with ignition on, engine off. Place to start, as if relays not clicking, dash switch is suspect.

Wife's 98 GMC Jimmy O.T.

Butch (PA)

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Bryan inIowa

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Anonymous-0

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buickanddeere

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ted regentin

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JDseller

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Butch (PA)

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Ron Anderson

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JayinNY

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VADAVE

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bradk

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RayP(MI)

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RayP(MI)

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