1998 Cheyenne K2500 4WD not engaging

Discussion in 'Transfer Cases' started by Joe Rack, Jan 17, 2021.

  1. Joe Rack

    Joe Rack Newbie

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    I bought a non-running truck a few months ago. Original engine was blown. Installed a rebuilt 5.7 engine a a couple days ago. The truck runs and drives well. I am working out a few kinks. One being the 4WD will not engage. This truck has the manual transfer case on the floor. I installed a new 4WD actuator, but nothing. I believe I have an electrical issue. Fuses are good. To my best ability, I checked all wiring harnesses for problems and wear, everything is connected and looks original. Oddly, (not sure if related) there is no power to the HVAC control panel. All other electrical components work as they should, no odd buzzing sounds.
    The truck was originally used by the US Forestry. I can see holes in the dash for a radio and maybe a light. I took the dash apart, but nothing was out of place.
    Any advice? What am I not checking?
    I appreciate any advice.
    Thanks,
    Joe
     
  2. Nad_Yvalhosert

    Nad_Yvalhosert I'm Awesome

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    Manually shifting the t-case internally actuates a position sensor, sending power to the front axle actuator.

    Electric: Check for power in, and power out of the position sensor on the t-case.

    Mechanical: Check to see if the t-case mechanically connects the front and rear drive shafts.

    Electric: If the power supply is good, check for power/ground at the axle actuator.

    You've got more things to check, huh.
     
    Last edited: Jan 17, 2021
  3. Joe Rack

    Joe Rack Newbie

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    I'm not great with electrical stuff, but I'll give it a go!
    Thank you for the advice! I will follow up.
     
  4. badco

    badco I'm Awesome

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    The switch that tells actuator to engauge is two wire behind where the front driveline comes out. I have a old pigtail the i plug into harness when mine acts up. My old 94 i had it on a rocker switch so i could use low range in 2wd
     
  5. Joe Rack

    Joe Rack Newbie

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    Well...I installed a new transfer case position sensor, but that did not solve the problem.
    Mechanically, the transfer case works fine.
    I tried to learn how to use a multimeter. Here is what I did and it may not be right, but I tried.
    As for power in: with the multimeter set at DC V, the center prong of the position sensor read 12v. the outer prongs were 0. (the ignition key was on and the transfer case shifter was set in 4H)
    I also tried to test the front axle actuator and found that there was power, but the number never settled down. Not sure, does that mean there is a problem?
    Lastly, I could not find where the ground wire would be for this.
     
  6. Nad_Yvalhosert

    Nad_Yvalhosert I'm Awesome

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    The 2-wire plug will have 12 v, key on. The other wire will be the output to the axle actuator. It will go 12 v when you shift into 4x4. Do you have 12 v on both sides when you shift into 4x4?

    The ground wire is on the back side of the front axle extension housing, passenger side, in the 2 plug connectors.
     
  7. Joe Rack

    Joe Rack Newbie

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    transfer case.jpg
    Is this the 2 prong connector you are referring to?
    if so, with the ignition key on and shifter in 2Hi, the green or blue-ish wire had power, the other wire did not have power. I then moved the floor shifter to 4Hi and the results were the same.
     
  8. Nad_Yvalhosert

    Nad_Yvalhosert I'm Awesome

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    No. That looks like the VSS. The one you want is on top of the case
     
  9. Nad_Yvalhosert

    Nad_Yvalhosert I'm Awesome

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    The one you want is about top center of the pic, about 2 inches from the vent tube

    main.jpg
     
  10. Schurkey

    Schurkey I'm Awesome

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    Unplug the electrical connector, unscrew the actuator from the front axle assembly. Actuator will be retracted. Plug the electrical connector back in, let the actuator hang from the wires.
    Photo 1. Retracted actuator. http://hbassociates.us/K1500_4WD_Actuator_02.jpg
    [​IMG]

    Start engine, trans in Park or neutral, wheels blocked. Put shifter in 4wd. Take your time, walk around the front, look at the actuator. Either the penis sticks out of the foreskin like it should, or it doesn't. (May take 30 seconds or a minute depending on temperature. Takes longer when cold.)
    Photo 2. Penis sticking out. http://hbassociates.us/K1500_4WD_Actuator_03.jpg
    [​IMG]

    If it sticks out like the one in the photo--about an inch more than before--your front axle needs work, or the transfer case isn't engaging 4wd.

    If it doesn't stick out an inch, the actuator is defective, or it's not getting power. Test for power and ground at the frame side of the electrical connector. Old actuators are like old men. They may not stick out as far as they did when they were younger.

    EDIT: My photos are for a thermal actuator. Your truck is new enough that it might use the motor-driven actuator. It should stick out, but it should move fast--way faster than the thermal units.
     
    Last edited: Jan 26, 2021
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