4 wheel drive shifting on its own! - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > 4x4 Drivetrain

4x4 Drivetrain 4x4 Repairs & Problems

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  #1  
Old 03-24-2006, 04:13 PM
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4 wheel drive shifting on its own!

This is my first time owning a 4 wheel drive vehicle.I just purchased a used 2002 Envoy and brought it in to be checked for this problem but they said they couldn't find a problem but its still happening.

First of all the dial is always set at 2 wheel drive. Then while slowing down or leaving a parking spot or going into a parking spot the light changes on its own to 4H drive. Can you imagine how hard it is to turn or how suprised I was when this first happened. Or I'm driving along and slowing down at a light and the 4H light is blinking, like its trying to engage. The 2 wheel drive only goes to 4H , not to A4 or 4L when this happens. I haven't experienced this while driving at a steady speed. Any ideas out there?

Thankyou Lisa(March)
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  #2  
Old 03-24-2006, 04:21 PM
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do a search on the 4x4 switch i think there is a fix for it
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Old 03-24-2006, 04:23 PM
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check this one out


http://forums.trailvoy.com/showthread.php?t=2529
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Old 03-24-2006, 04:58 PM
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Different problem

Quote:
Originally Posted by 03slt_soccal
I went to this thread but my problem is a little different. I'll try to explain a liitle better ...2H, A4W, 4H and 4LO all work fine. The roads are dry here(canada, hard to believe) so I leave it on 2H......then all of the sudden while slowing down or turning in or out of a parking positon the 2H light switches to 4H stays on for a few seconds and you can feel that it has engaged and it is in 4H drive(can feel the steering tightening up)..then it switches back to 2H. THis does not happen all the time it happend last night while leaving the mall . The time prior to this was around 2 weeks ago. I also looked up "4x4 switch" but that is different also.
Thanks for you suggestions...Lisa(March)
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Old 03-24-2006, 05:12 PM
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FWIW, you may want to ask your service rep to have the vacumn actuator switch ( near the transfer case, not the one in the dash ) checked. On the older s blazers that used electronic 4x4 switches, the actuator would develop a leak, which would cause the exact symptoms you describe during low speed maneuvers which would cause a shift of the actuator assembly. You may also want to check and make sure that all the vacumn hoses are connected in your engine bay. Your comment of it only happening from a stop to turn or low speed may be the clue.
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  #6  
Old 03-24-2006, 08:17 PM
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Quote:
Originally Posted by tb05
FWIW, you may want to ask your service rep to have the vacumn actuator switch ( near the transfer case, not the one in the dash ) checked. ..
AFAIK, it's all electronic on the TB's. To test, put the key to on or run, you should be able to hear the electric front axle disconnect (shift on the fly actuator) buzz and click between 2wd and 4wd mode. There is also an encoder motor in the xfer case that engages/disengages the xcase output. You cant hear that one as you need to be moving for that one to work.

Joel
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Old 03-25-2006, 12:15 AM
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Thank you!

Thanks everyone for the information. I'm bringing it in to be checked once again...........on Wed. March 29th.....wish me luck...

Lisa(March)
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Old 04-03-2006, 09:46 PM
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Still have not fixed the problem/new discovery

I had to cancel last Wednesday appointment but I brought it in today. Once again they checked it and still have not found the problem. The mechanic said he found this problem once before when the lights would change from 2hi to 4hi etc. but the 4 wheel drive never actually changed only these lights so they changed the transer switch and it corrected the problem. Of course I have to pay the $100 deductable.They asked me to come back tomorrow and the top guy will be in and they want me to explain everything that has been happpening with the 2hi,4hi drive etc. Funny thing when I started the truck just after they had checked it a second time I noticed all the lights flashed on, on the transfer case then went solid to 2hi which it was set at....this has never happened before as soon as I got home I looked in the manual and this as you all probably know is what is suppose to happen everytime I turn on the vehicle.I read that manual but must have missed this. Do you think they may have reset the computer controls or pulled out the fuses and put back in and now its working properly? Maybe the problem is fixed. I will mention it tomorrow to the top man that the transfer case was not lighting up like that before. I'm surprised the mechanic never saw this before...I didnt even know those lights should flash at start up. Since the problem I have only happens occasionally I would have to continue to drive until the 2hi switches to 4hi on its own to see if that problem still there and that the lights flashing at start up has actually corrected the problem...anyone want to comment on this new discovery???

thanks lisa(march)
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  #9  
Old 04-03-2006, 11:39 PM
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Ask them to hook up a data recorder to your vehicle for a few days so they can record what is going on.
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  #10  
Old 04-05-2006, 09:53 PM
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replaced transfer switch

well they replaced the transfer switch. so i'm hoping this has solved the problem.
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