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96 GMC won't go into 4wd

Discussion in 'Truck & Equipment Repair' started by 08f150, Feb 26, 2010.

  1. 08f150

    08f150 Member
    Messages: 33

    Just wondering if anyone has any experience or ideas here. Have a 96 GMC 2500 7.4L, auto trans and electronic transfer case. Last night it blew the fuse for the 4wd. When I push 4Lo I can hear the transfer case move but then the fuse blows and it never goes into 4Lo. Normally the light on the button blinks for a couple seconds then goes on steady. Now it just blinks and never goes steady.
    I looked around briefly and couldn't find any frayed wires or loose connections.

    Any ideas??
  2. k5PlowGuy

    k5PlowGuy Member
    Messages: 40

    Sounds like the transfer case may be toast. If you don't see anything obvious I'd say take it to a dealer or rebuilt the trans case if you are familiar with the workings.
  3. mycirus

    mycirus Senior Member
    from Mass
    Messages: 589

    If he is blowing a fuse sounds like there is a short somewhere. I would inspect and look for a grounded cable 1st.
  4. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Disconnect the electrical connections at the front axle actuator. Now try the dash buttons. See if you can hear the transfer case shifting, and hopefully you will stop blowing fuses. If that's the case, sounds like it's time for a new front axle actuator. If you need to get rolling right away, you can pull the actuator from the axle, put a lugnut or short socket in the cavity, and thread the actuator back in Do not re-connect the wires. Now the axle is always locked in, and you will have instant 4wd. I have been running my truck this way all winter and love it.

    NICHOLS LANDSCA PlowSite Veteran
    Messages: 4,362

    Encoder motor on the transfer case is bad
  6. sjcolwell22

    sjcolwell22 Junior Member
    Messages: 7

    I would check the wirng from the transfer case up . looking for chaffed wires . There is an electric shift motor on the transfer case that do go bad. But deffinatrely check the wireing first i had a motor go bad in the past. I dont think its the front axle shift actuator.
  7. the_experience

    the_experience Member
    Messages: 75

    This was my first thought too. The flashing lights mean the transfer case control unit has seen a fault. The encoder motor will keep moving and trying to shift until it receives a signal that it has turned far enough from the encoder. If the encoder fails it won't know and it will dead head against a mechanically locked t-case until the fuse blows. The tip on checking the actuator is also very valid. Failure of both parts is pretty common.
  8. redsled

    redsled Junior Member
    Messages: 7

    front slug is junk?

    found if fuse popps check front slug foung it overheated and had a large draw when called for. it was the same year and model as yours. hope this helps