96 Chevy 4wd won't engage

Moline_guy · Oct 29, 2013

Had 4" of nonsense last night, haven't used 4wd all summer. The 4wd light flashes but doesent stay lit and 4wd isn't engaging. I don't hear any chatter. When switched to 2wd the light for 2wd stays lit. This is the push button type swith. I tried 4 low and the transfer case switches but front axle still doesn't engage, any ideas where to look first? Thanks for any help or information.

MSM · Oct 29, 2013

Probably the actuator for the front axle. Check the wiring for the actuator first.. brush and cornstalks can knock the wiring loose. If the wiring is good and you have 12 V to it when the 4wd is engaged, then the actuator is likely bad.

Dr. Walt · Oct 29, 2013

My 88 GMC 2500 4x4 does the same thing whenever it gets really cold outside. I just drive forward & backward a few times while holding the front drive lever down. When it engages I hear a definite "thunk" and the 4 wheel drive light stays on steady.

chevytaHOE5674 · Oct 29, 2013

IIRC 96 would have came with the thermo type front axle actuator. They aren't very reliable. You can replace it with another thermo unit only to have issues down the road.

Or you can upgrade to the better electric style actuator, it requires a little wiring change and a steel spacer to be added.

Kyle in KY · Oct 29, 2013

Check the voltage as stated above, but most likely the actuator is full of crud. Majority of the GM's I've worked on the actuator plunger and rod need cleaned and lubed. Usually work fine after a little cleaning.

farmer boy · Oct 30, 2013

Likely has a thermal actuator. According to the notes on rockauto, the change from thermal to electric was made 12/95. Check the build date on your truck. Chances are you have the thermal actuator, because the electric actuators cause very few problems. The thermal actuators on the other hand, are garbage.

Nancy Howell · Oct 30, 2013

You got that right. My 96 4x4 almost never engaged. Gave up even trying.

Jon Hagen · Oct 30, 2013

If the thermal actuator is bad, do yourself a favor and convert to the motor actuator type. It will lock the front axle in under two seconds,VS the thermal actuators up to 1 minute to lock.

What good is that slick "shift on the fly" transfer case when the front axle will not lock for nearly 1 minute. Makes them the 4WD they should / could have been from the start.

Bob · Oct 30, 2013

MANY of the older ones have been changed over... that requires a new-style (motorized) actuator and an add-on wiring harness. (DORMAN Part # 600600, for example) that has to be run back to a switch on the transfer case.

<img src = "https://www.rockauto.com/getimage/getimage.php?imagekey=1268524&imageurl=http%3A//www.rockauto.com/info/RB/600-600-003.jpg">

That can be done back to the first ones, from '88.

96 Chevy 4wd won't engage

Moline_guy

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MSM

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Dr. Walt

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chevytaHOE5674

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Kyle in KY

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farmer boy

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Nancy Howell

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Jon Hagen

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Bob

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