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2002 gmc envoy_slt_xl
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My 2002 Envoy will jump out of 2WD and into a sort of neutral position almost randomly. Moving it to A4WD (after turning off the engine to avoid grinding) will correct it and even allow me to return to 2WD (or 2HI - I don't recall what it says). This is more frequent in the cold weather especially after a cold start but it will happen even while I am driving when everyting is warm. It did this once or twice last winter and is doing it almost daily this winter (20K miles later).

The 4WD system works OK otherwise however the light has flashed intermittently since I got the vehicle even in the absence of the problem above. It has also failed to move between the ranges while the light was flashing but this always seemed to resolve itself. The transfer case fluid is fresh. The vehicle has 114K miles.

Any ideas would be appreciated.

John
 

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2005 chevy trailblazer_lt_ext
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Same thing is happening to my 2005 TB. I will be in 2hi and the A4WD light will flash a few times, then the truck does a quick single jerk (not very intense, but noticeable) and stays in A4WD. If I slow down to below 55, put it in 4hi, wait a minute, then back to 2hi, it goes away for that leg of the trip. As soon as I restart and go again it will do the same thing. Just satrted happening since the weather has been cold. Not sure if it is related... Wondering if anyone has a fix??

Thanks!
 

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2004 gmc
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26,181 Posts
... Wondering if anyone has a fix??
I'd try a new switch first. They seem to fail more often than they should. GM # 25827385 $28 list, $20 plus shipping at parts4chevys.com Getting the dash out to change the switch: http://forums.trailvoy.com/showthread.php?t=6459

My 2002 Envoy will jump out of 2WD and into a sort of neutral position almost randomly.
Do you mean neutral as if the transmission isn't engaged and the vehicle won't drive? That's much more serious. If you just mean an indeterminate 4WD mode, I recommend trying the switch as well.
 

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2002 chevy trailblazer_ls
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Hello, new to forum, seems like a lot of info here. My 02 Trailblazer transfer case when in 2HI seems to randomly drop into neutral at any given time. May be traveling down the road at 40mph and will happen. No forward drive then. Move the selector switch to A4WD and it re-engages. Now may resume driving. No odd switch lights, all drive ranges work. Transfer case does not completely go into neutral when selected by the switch.
 

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2004 gmc
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26,181 Posts
Welcome!
My 02 Trailblazer transfer case when in 2HI seems to randomly drop into neutral at any given time. May be traveling down the road at 40mph and will happen. No forward drive then. Move the selector switch to A4WD and it re-engages. Now may resume driving. No odd switch lights, all drive ranges work.
What is the mode switch light display when this happens? Does it stay steady at 2HI?
Transfer case does not completely go into neutral when selected by the switch.
What does this mean? When you WANT it to go into N it won't? It stays in 2HI? What does the mode switch light display when you try to go into Neutral?

Neutral mode is what happens when the switch wiring goes to a high resistance, so it might be a switch, harness or TCCM problem. All depends on what the lights display.

How often? Once a month, week, day?

How are you sure it's the transfer case dropping you into neutral and not the transmission? Does it recover while you're driving by just turning the mode switch to A4WD and back, or do you have to coast to the side of the road and stop and restart the engine?
 

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2003 chevy trailblazer_ls
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1,708 Posts
Roadie mine has been funky with 4x4lo, 4x4hi and awd when it gets in the 20's this year. If I drive it for a few miles in 4xanything all seems to work ok. When it warms up to 60 or so all works fine. As soon as it gets warm enough I plan on cleaning the grease out of the (what ever it is called that moves the clutches in the transfer case) Talk later about this.
 

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2002 chevy trailblazer_ls
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2 Posts
Roadie, the 2HI light remains steady. When trying to shift the transfer case to neutral, the shift is attempted but will not quite complete, the gears will create a grinding noise. However, the red N will light as if the change was successful. The transfer case disengagement has been happening randomly since 4wd was used for the first time back in December. I believe it is the transfer case because under any of the circumstances when the perceived neutral condition is experienced switching to any other position on the 4wd switch corrects the issue. You never have to restart the engine.
 
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