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Four Wheel Drive Acting Funky

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by daman4469, Dec 26, 2012.

  1. daman4469

    daman4469 New Member

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    Hi guys,

    I have a 2000 silverado Z71 4WD. I was driving up to the local ski resort the other day and kicked it in four wheel high. The roads were snow covered. I drove a little ways and noticed the 'Service 4WD' light came on. Afterward, it would not kick out of 4 High until I shut off and restarted the engine. I noticed this problem at the Outer Banks this summer using 4WD there as well, and took it for diagnosis, but no errors were found, even with that light on. Any ideas? It kicks in and 4WD works, it just doesnt want to come out after that light comes on. I had it happen before where it would not come out unless I disconnected the negative battery terminal as well. Also, it sometimes seems like it physically comes out, but the display on the push buttons doesnt show it, it still shows as being in 4WD. Any ideas would be great.

    -Rob
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  2. thrasher

    thrasher New Member

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    Did you put it into/out of 4x4 while in drive? Sometimes they'll hang up it the truck is in gear. I usually shift into neutral to do that. Actually, my truck will only shift into 4lo if it is in neutral, it won't do it if it's in park.
    It could be the actuator or maybe the transfer case needs oil or an oil change.
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  3. dsfloyd

    dsfloyd New Member

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    I know that encoder motors caused issues with those. It's push button correct?
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  4. RayVoy

    RayVoy Active Member

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    Yeah, they do. Sometimes, if your real lucky, changing the t-case fluid will give new life to the encoder motor (it needs to move clutch plates).
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  5. daman4469

    daman4469 New Member

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    Yes, its push button. Its definitely working, but something within the computer it seems gets wacky.

    I had a new transmission put in about a year ago, would the transfer case fluid have been changed? I know the transmission/differential fluid was changed.

    If I have to, I'll change that fluid myself...never messed with it, could be empty as far as i know....is it easy to do?
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  6. RayVoy

    RayVoy Active Member

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    Two separate boxes, unless instructed, I doubt the t-case fluid was changed.
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  7. j cat

    j cat Active Member

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    the transfercase fluid is blue in color. as the fluid gets damaged it turns gray . this is when it should be replaced. the tracII GM fluid must be used. this has the proper fluid to operate this transfercase. on my 2000SIL I do this every 30-40,ooomi. at this point for me its starting to turn gray.

    the push buttons should flash 3-4 times into and out of 4wd/auto 4wd to 2WD. the longer it flashes this would indicate that the encoder motor is binding. clean fluid should fix it.

    open the top fill plug first then open the drain plug about 2-1/4 QTS required.

    use thread sealant on the plugs. torque to about 12 ft lbs. never over torque because the case WILL CRACK !
    #7
  8. RayVoy

    RayVoy Active Member

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    Good advice [MENTION=39185]j cat[/MENTION], you always want to know you can put fluid in, before you take the old fluid out.
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  9. Kady

    Kady New Member

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    What happened when you would push the button? Did it flash at all? Or remain solid as if you hadn't even pushed it? If it flashed, thats one thing.. But if it didn't, its most probably your selector switch on your dash... 50 bucks gets you a new one. Easy to install... My truck did the same thing... When the service 4wd light is on, I can't change it at all. Doesn't even recognize the buttons being pushed...
    #9
  10. daman4469

    daman4469 New Member

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    @j_cat , excellent....I'll do it once there is a break in the weather. Good advice, and I thank you...even if it doesnt fix the issue, its probably a good thing to do anyway. [MENTION=24589]Kady[/MENTION] , yes, my issue is quite similar. Once that 'Service 4WD' light comes on, the buttons are useless and do not respond at all. I'm thinking I may be in the same boat. However, I'm curious as to why the service light is coming on to begin with. I think jcat's idea will help with that part. (Hopefully, fingers crossed). I think it will.
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  11. Kady

    Kady New Member

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    The buttons are known for being junk... Some people recommend cleaning the connections or re-soldering to fix the problem... The part is cheap enough, and simple to install...


    http://www.youtube.com/watch?v=Y9hRssZApy8
    #11
  12. Pikey

    Pikey Moderator

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    If you had the trans done last year, I would crawl under the truck and check out the connections around the Tcase. I bought a used 2003 yukon xl that had a trans replaced a year before. One day while driving the service 4 wheel drive message came up. The buttons became useless! I crawled under the truck and found a connector that the trans shop did not put the locking pin back thru. I pulled the connector apart, then pushed it together, put the pin in and the message went away. It never came back.
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  13. daman4469

    daman4469 New Member

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    I'll have to check that while im changing fluids. Im not real familiar with the underside, as shes been pretty trouble free. [MENTION=24589]Kady[/MENTION] awesomme link. thats exactly my issue! Curious as to what a shop would charge to change the fluid. Weather here in central pa is COLD and snowy, and I have no garage, so getting this done myself may have to wait a while :)
    #13
  14. j cat

    j cat Active Member

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    I have repaired the 4wd select switch. solder joints were not properly done [cold].

    with this failure the 4wd light comes on when driving in 2wd normal driving conditions. then on restart is off until some time in the new driving cycle it may come on again.

    this is because the PCM is programed to run on board system tests. like the fuel evap system etc.. when this 4wd control system is checked the switch circuits are monitored and if it is incorrect the service 4wd light comes on. or if any other component in the 4wd system is in error.
    #14
  15. Kady

    Kady New Member

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    So swapping out the switch helped you too?
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  16. a.graham52

    a.graham52 New Member

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    in my experince a bad switch will cause the light to come on. i do not remeber the code in the transfercase date but its there.
    #16
  17. j cat

    j cat Active Member

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    what I did was re solder the joints on the circuit board/switch . very easy with the correct soldering iron.takes about 30 min. most would just replace the switch but are those solder joints good ????

    I believe its cost is about 40.oo...

    this was done many years ago. that was the only problem I have had with the drivetrain. about 40,ooomi.just out of warrantee.
    #17
  18. daman4469

    daman4469 New Member

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    Just as an FYI, I replaced the selector switch and changed my front transfer case fluid. Ran it in the snow for a couple miles with no error. Resolved. Thanks a MILLION!
    #18
  19. j cat

    j cat Active Member

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    the switch even if it appears to work will throw this service 4wd light. this is because the computer does a diagnostic check of this component. if the solder joints are bad even if not in 4wd , the service 4wd light will come on...many have had this occur.. the switch solder joints are a widespread GM defect. soldered in Mexico !
    #19

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