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  1. #1

    Default 96 k1500 4wd mystery

    Ok, this is my first post here, so be kind
    i have read many, many posts about getting 4wd fixed on these trucks and so far I cannot find my exact problem.
    here is what I have.
    96 k1500
    push button 4wd. When I push the button for 4hi, I hear the t-case switch and the front shaft turns, but the light just blinks, so it looks like t-case is fine.
    i replaced the actuator on the front end,only To find that there was a corroded terminal on the t-case switch, which I replaced.
    When I push the the 4wd button I don't get 12v to the actuator, but if I take the t-case switch off and manually move the ball on it, the actuator gets 12v.
    So the problem seems to be with a vacuum(?) in the t-case?? I cannot seem to find any diagrams or anything on this anywhere. If anyone has any suggestions, I would be grateful. This is just my kick around truck, so I don't want to spend a buch of $ at the shop, but I would like 4wd to work for winter.

  2. #2


    The GM manual has wiring schematics for this system and a short explanation of how the system works. Most shops have wiring diagrams by Mitchell , an will usually print one for you. I found that GM uses modules for all systems located behind the instrument cluster. I think the 4 wheel module is located above the heater, just pop out the glove box.

    I would start by checking all wiring for damage and dirty connections. You could test the actuators by applying power.
    Often one will find the problem with a good visual inspection. Good Luck

  3. #3


    I had a '96 Blazer, it may be similar. It used a vacuum motor to operate the front passenger side axle disconnect. The vacuum motor was mounted in the engine compartment, near the lower mounting bracket for the rad. The motor was connected to the disconnect with a shaft, or maybe it was a cable.

    The newer trucks use an electric motor to operate the disconnect, in these models, there is an electrical signal returned to the transfer case controller when the motor has engaged the disconnect. I don't remember if the vacuum operated units have this return signal.

    Water is the biggest (IMO) problem with these t-case electrics, try a good cleaning of all electrical connections around the t-case and disconnect actuator.

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

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