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94 GMC 4 wheel not working

Discussion in 'Truck & Equipment Repair' started by Eastside Eric, Dec 13, 2010.

  1. I have a 94 GMC and the 4 wheel worked all night but I turned it off for about an hour and when I got back in 4 wheel was out. I can put it in neutral and back into 2 wheel but when I shift it to 4 it does not work. Any ideas of what is going on?
    Thanks in advance.
  2. bill7101

    bill7101 Member
    Messages: 34

    I would check the front axel actuator, they like to go out on these trucks, expecially if its still the thermal one that heats up to actuate, and if its cold it takes longer to actuate the axel, have to crawl under the truck and see if the actuator plug has power and ground to it when its put into 4wd
  3. ArcticTahoe

    ArcticTahoe Junior Member
    Messages: 14

    if you can get the truck on a lift unscrew the actuator put the truck in 4x4 and push in the pin manully with a screw driver if it goes into 4wheel the actuator or wiring is your issue but ive seen l;ots of thses as plow truck grenade front diffs so check out the mechanical workings of the 4x4
  4. b&b landscapes

    b&b landscapes Member
    Messages: 74

    The most notorious thing these trucks (especially 94) is the switch on the transfer case goes out.......
    and its a @$#^% to get to, when our truck did this heres what i did and you can test this way

    TEST: Lay in front of truck in a quiet garage and have someone turn key to on postion, and put truck in 4H and listen for the actuator to move (you will here it)... if you dont hear it then do this: run a wire from the battery to the actuator and shave the power wire on actuator and touch the battery wire to it and listen for the actuator to move (you will here it). If you still dont hear it the actuator is bad, if you do hear it then the switch on the transfer case is bad

  5. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    My bro-inlaw has the exact same truck. It was the thermo actuator
    on the front axle. We meet for breakfast after a big storm and he was complaining about no 4X4. Well duhh, check the thermo actuator on the front axle. The poor guy is helpless when it comes to repairs! I keep telling him PLEASE call me before you pay to have it fixed! I got tools and a welder, we can fix most stuff. It's great when he hands over a case of Budwiser too. It's worth my hour of labor.
  6. IMAGE

    IMAGE Sponsor
    Messages: 1,736

    If it is a bad actuator, you can just put a big nut in there as a spacer to manually lock it in to get you by. It makes the front axle always engaged, and the tcase lever will still control if you are in 4x or 2x. I used a lug nut, and ran it for over a yr like that.

    Its really easy. Screw the actuator out. Put a roughly 3/4" spacer in the hole (again I used a lug nut), and screw the actuator back in. If the spacer is to long, the actuator will not screw all the way back in. If the spacer is to short, it will pop out of 4x4.
  7. sbt1

    sbt1 Member
    Messages: 59

    That thermal actuator has to be the worst design ever.
  8. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    The colder it is the slower it engages. They forget about this. I have seen a few guys that get into trouble when they forget this. DOOH, no 4 wheel drive, up on a snow bank!
  9. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    I run a spacer in mine all winter. The instant 4wd is fantastic.