Four Wheel Drive Acting Funky

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

  1. daman4469

    daman4469 New Member

    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.

  2. thrasher

    thrasher Rockstar 100 Posts

    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.
  3. dsfloyd

    dsfloyd Epic Member 5+ Years ROTM Winner 1000 Posts

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

    RayVoy Epic Member 5+ Years 5000 Posts

    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).
  5. daman4469

    daman4469 New Member

    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 it easy to do?
  6. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

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

    j cat Epic Member 5+ Years 1000 Posts

    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 !
  8. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

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

    Kady Epic Member 5+ Years GMTC Chick 100 Posts

    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...
  10. daman4469

    daman4469 New Member

    @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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