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4 wheel high not engaging help

Discussion in 'Chevy Trucks' started by perfect storm, Dec 13, 2005.

  1. perfect storm

    perfect storm Junior Member
    Messages: 8

    I have a '97 GMC Sierra 4x4 that will only go into 4 low and not 4 high. None of the indicator lights on the dash are lit when in 2 wheel drive but blink when 4 low is engaged. My mechanic replaced the actuator switch but that didn't work. Any help would be appreciated. Thank you
     
  2. neetchracer

    neetchracer Junior Member
    Messages: 26

    It is more than likely the actuator, but could be the TCCM(transfer case control module). I usually quote the higher priced unit, usually around $400, and if that does not fix it I swap in the other one and 99.9% of the time that will fix it. That is one plus of taking it to a dealer with parts on the shelf. I am unaware of a better way to diagnos the transfer case. Thats the best I can do without testing it myself.
     
  3. perfect storm

    perfect storm Junior Member
    Messages: 8


    Thanks . I guess it has to go back to the shop . I just wanted some advice on things to look for . weird that it will go into 4 lo but not 4 hi
     
  4. JMR

    JMR Senior Member
    Messages: 567

    Besides the wiring there are 5 parts to the system. The dash switch assembly, transfer case shift control module located under the dash, the encoder motor on the transfer case, the transfer case switch, and the front axle accuator. Had one in last week............did exactly as you describe. The customer had replaced the shift module and the encoder..........turned out being the transfer case switch. Located on the transfer case, part # 15693423. Good luck.
     
  5. perfect storm

    perfect storm Junior Member
    Messages: 8

    Thank JMR this is the kind of info i am looking for . I appreciate the input
     
  6. neetchracer

    neetchracer Junior Member
    Messages: 26


    Sorry, I didn't mean to confuse anyone, but you can count the t-case switch, and front axle actuater out because you said it goes into 4 low. The dash switch has already been replaced. Only two items left, and if anyone has a good way to isolate which component has failed I'm interested. I have followed the diagnostic charts in service manuals and they don't help either. Good luck.
     
  7. neetchracer

    neetchracer Junior Member
    Messages: 26

    I just realized you said it just blinks in 4 low, if it does not blink in 4 high I will stand by my last statement that is it actuator or TCCM.
     
  8. JMR

    JMR Senior Member
    Messages: 567

    WRONG......the one I just repaired had been to the dealer twice. It did the same thing. Worked fine in 4-low, but no 4 high. the switch in the transfer case was BAD. Trust me on this one. I've owned a repair shop for the last 21 years. DON"T rule out the switch. Because it goes into 4 low ONLY proves out the front axle actuator. The dealer missed diagnoised this twice, that is why it ended up at my shop. My lead tech has been working for me for 20 years and often the dealers send strange problems to us they can't figure(that's supposed to be a secret).
     
  9. perfect storm

    perfect storm Junior Member
    Messages: 8

    Well, whichever it turns out to be I will be sure to let you know . I appreciate the input . the first shop I went to was charging me to diagnose the problem and didn't fix it , so i went to a friends mechanic who doesn't charge to diagnose . He replaced the dash switch and said the actuator was working but that is where I gave up on him to ask you guys . I will go back now with at least a bit of ammo to have him check out.. thanks again
     
  10. Chevman

    Chevman Junior Member
    from NE PA
    Messages: 21

    Just a thought but my truck did that to me last year and all it was is the dash switch.
     
  11. perfect storm

    perfect storm Junior Member
    Messages: 8

    already replaced it chevman.
     
  12. neetchracer

    neetchracer Junior Member
    Messages: 26

    So what fixed it? Is it fixed yet?
     
  13. perfect storm

    perfect storm Junior Member
    Messages: 8

    sorry it took so long to get back to you on this one .. It is still not fixed 800 bucks later .. replaced the transfer case encoder , t case switch , dash switch .. the mechanic said on the lift it goes into 4 high but with the weight of the truck it wont go into 4 hi .. they said the only thing left to replace were the bushings in the xfer case. already in over a grand with no improvement .