1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

91 Gmc K150 4x4

Discussion in 'Truck & Equipment Repair' started by zago7, Aug 4, 2006.

  1. zago7

    zago7 Junior Member
    Messages: 5

    Hey guys I'm new here great board!
    When I cold start my truck the 4X4(floor shifter) kicks in right away
    When I take the 4X4 off to 2wd after plowing for about an hour
    and then put it back into 4x4 about 10-20 minutes later it won't go back to 4wd
    I have to wait at least an hour or two before it works again any ideas why?
    I do this because I've been told that it's not good to have the 4x4 on when the roads are clean, and driving on straight ashphalt,
    Should I keep the 4x4 on at all timesthanks
  2. Sharpshooter77

    Sharpshooter77 Senior Member
    Messages: 162


    Well I can tell you that if your truck has selectable 4wd hi and low and 2wd. You should use 2wd when you are on dry,paved road. Plus if you do keep your truck in 4wd when your in normal every day driving condtions it will cut your gas mileage down and increase the wear and tear on your tires, And the other 4wd componates. The 4wd would be more effectively on dirty/muddy roads, plowing and any thing that your 2wd can't handle. As for T-case taking a while to shift in after the truck has warmed up. You should check your T-case fulid levels and make sure that you have the right grade of fulid in it. Hope this helps you out.
  3. rleerodgers

    rleerodgers Junior Member
    from Georgia
    Messages: 2

    On a 91 with a new process when the shifter is put int 4wd hi it mechanically shifts the transfer case into 4wd and closes a switch that sends current to the thermal axle actuator on the right of the front differential. This heats the gas in the actuator to push the piston that pushes the shift fork to lock the axle. When the axle fully engages it turns on the 4wd light. You probably have a bad actuator or a binding one.
  4. blee1ash

    blee1ash Senior Member
    Messages: 107

    I would bet money that it is the thermal acutator. GM has an updated one that will engage much faster than original. The original take 20 - 30 seconds to engage the updated ones engage almost imediatly. They are relativly easy to install and come with instructions, the only installation diffrence from the originals is that you have to splice into a wire by the transfer case.
  5. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Check all your wires leading to the thermal actuator too. A buddy of mine replaced his and still had the inconstant engagements. It ended up being the wiring on his GMC.
  6. zago7

    zago7 Junior Member
    Messages: 5

    Thanks for the help guys!
  7. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Some of the guys I have talked to also notice that the older GM's engage slower when it's really cold out. It might be a problem if you need it in 4X4 on hills etc and it's not engaged the axle yet.
  8. bassfearmee

    bassfearmee Junior Member
    Messages: 7

    Thermal Actuator

    I had an 89 2500 series with the same problem....the engineers at GM came up with a replacement actuator in 1995 due to this problem...the new actuator is not a thermal, it is an actual electric actuator that is very easy to install. Get up underneath the truck and locate the front transfer case, just to the right passenger side is a small screw in plug that has a cable hooked up to it. Remove the cable, unscrew the actuator, replace and reinstall the cable. This should fix the problem for good.
  9. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    and if you want to realy know when its in or out. get a 4x4 posi lock kit. replaces the actuator and gives you a cable to pull.http://www.4x4posi-lok.com/app_chevy-k.html can be had for a few buck less at other popular sites.