Service 4WD...Need help

Discussion in 'General Chevy & GM Tech Questions' started by Dented Fender, Dec 29, 2010.

  1. Dented Fender

    Dented Fender New Member

    Newbie here, just joined about an hour ago after reading quite a few interesting posts... i figureed I'd ask a question and see if i can get some useful input!
    I drive a 1999 silverado 1500, and believe it or not; I am having problems with my 4 wheel drive. First off, I am 100% positave that it has nothing to do with the push button switch on the dash. Anyways here's the deal. Sometimes (maybe 30% of the time) when I start my pickup the amber colored light on the 2hi button is lit up, and I am able to switch between 2hi and auto 4wd. However, I am not able to get it into 4hi. The light on 4hi just flashes at me about 5 or 6 times when i press it while 2hi is lit up, then 2hi flashes 5 or 6 times then stays solid. The service 4wd message does not show up.
    The other 70% of the time or so is a differnt story. As soon as i turn on my key on, the light on the auto 4wd button flashs for a fraction of a second and then i can hear relays behind the dash start to click. they click about 10 times and its almost to a rythem (im serious). Then as soon as i start my pickup they start clicking again, and then service 4wd comes on.
    I recorded videos and posted them on youtube. The first one is a video of when i am able to switch from 2hi to auto. this is the link The second video is when the service 4wd message comes on and you can hear the strange relay clicks. there's that link

    Can somebody please let me know if they have heard of the same problem. I really dont want to go to the bank and refinance my pickup to buy a new TCCM and a new encoder motor or a new transfer case if i dont have to. Thanks for any help
    Last edited: Dec 29, 2010

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