Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum - View Single Post - Can 4WD be non functional?
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Old 07-17-2017, 03:39 PM
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2004 Chevy TrailBlazer LS EXT
Liquid Silver Metallic 4.2L I6 4X4
Join Date: Oct 2009
Location: NY
Posts: 43
Originally Posted by the roadie View Post
Welcome! This system is my specialty. There are two motors that work to engage 4WD. A front axle actuator that engages a splined collar on the passenger side CV shaft, and an encoder motor that moves clutches and gears in the transfer case. Each of them has a distinctive sound that can help diagnose failures.

But not yours. That trick only works if you get the Service 4WD light on, because the TCCM (transfer case control module) is looking at feedback signals on each of those motors to confirm that they moved to where the controller commanded them.

Your failure is much more likely to be mechanical. The cheaper of the two is the front axle splined collar that the actuator presses on. To confirm this, jack up the front of the vehicle, both sides on jack stands, put it in 4HI and listen to the motors whine. Confirm it's in 4HI and the light on the mode selector switch goes steady. Then turn the driver's front wheel. If the opposite one turns backwards, then the actuator is working and the problem is in the transfer case. If you can spin the passenger side front wheel freely, then the problem is in the actuator.

Some folks have done this work themselves - some pay mechanics. Let us know what the experiment tells you and we can advise further.
A4wd works but 4hi and lo do not.
I as y stated. Both wheels turn in opposite directions when you spin them in 4hi so it is engaging.
Both actuators make noise, the transfer case one is only a few years old.

Now this only seens to happen in the winter time when its real cold.
The selctor switch lights up as it should, tho on occasion the lights will blink then go out. If i put it in nuetral while stopped the bliniking light will go solid as if it is working correctly.

I was told the actuator on the pass side could be freezing up but idk how true that is.

Where to go from here?
As stated a4wd works flawless. The hi and lo during very cold moths doesn't.

04 ext TB 4.2l.
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