4WD Actuator Redneck Fix

Discussion in 'Transfer Cases' started by RustyTruck, Jan 14, 2018.

  1. RustyTruck

    RustyTruck Newbie

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    Sep 23, 2017
    I am new to this forum, so please forgive me if this write-up is subpar...

    I decided to put this in the transfer case section instead of the axle section because that's where everybody looks when the 4WD stops working.

    This is an explanation for those who have problems with the 4WD actuator in the front differential, and need a quick fix. I was on a trail, and the wires got ripped out of my actuator. I use 4WD a lot, and decided this route was the best for my scenario. The stock actuator is crap IMO anyway...

    Simple explanation first:
    The 4WD in these trucks uses what is known as a thermal actuator. It is located in the front differential, and engages the front wheels (not a locker) to the driveshaft that goes to the transfer case. This does not engage 4WD! Only when your transfer case is engaged, and your front differential is engaged do you have 4WD. For those of us lucky enough to have a manual T-Case...this fix gives you immediate 4WD when you engage the T-case, for relatively no cost. There is a better option out there (4x4 Posi-Lok), for anyone looking to keep their truck nicer. I have a beater, and saw no point in spending $150.

    You will need:
    A crescent wrench
    A socket about 1" Long
    A jack
    Half a beer(It doesnt take long enough to drink a full one)

    First thing is to break loose the thermal actuator. Mine was really easy, and I had no problem using a crescent wrench. Others may be more difficult. You can see I did that here:

    You will then need to Jack up one wheel, to allow the differential to spin. There is a set of "gears" that need to mesh, and probably won't line up without motion, or the ability to move. This is why guys burn up their actuators when they engage 4WD and don't drive...


    You will then need a socket, or piece of pipe roughly 1" long. I used some craptacular 7/8s socket I had laying around from the harbor freight.

    Remove the actuator


    Then take your old greasy socket(I already had it in my differential, hence the grease...)


    And slide it into the differential. Then replace your actuator, and give it a good snug twist (no idea if there is a torque spec, and frankly I didn't care) with your wrench. Turn the wheel that is off the ground and your front driveshaft should turn, and vice versa.

    I hope this write-up helps those of you looking for a way to fix the OEM actuator, without spending money.

    Since I am new, and this is my first write up I would appreciate constructive criticism on what I can improve on. If anyone believes I am giving misleading or un-wise information, please feel free to say so, however I do not take responsibility for anyone ruining their front differential if it goes wrong.
    RichLo likes this.
  2. Mule89

    Mule89 OBS Enthusiast

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    Aug 14, 2016
    Hamilton, Ohio
    I found this useful if I ever have a 4x4 obs I already knew how to do a similar thing on S10 trucks
  3. RichLo

    RichLo I'm Awesome

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    Jan 6, 2015
    Nice!! I'm going to have to do this to my plow truck this summer if it doesn't fail before then. Thanks for the write up!!!
  4. RokRoland

    RokRoland Newbie

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    Dec 28, 2017
    Hi, I'm new too, and just put a Standard thermal actuator in and it came with instructions, which I found after installing. However, I presume the socket you used did not come with application specific instructions so I learned some things which might be useful in this context.

    According to the instrction, the torque spec is 15 ft-lb, which equals 20 Nm. The instruction states to use a sealer on the actuator threads. I did not, because I read after installing, at least it will be easy to pull out the actuator and put some sealer in.

    As other practical notes, if replacing the actuator wire anyway, be careful not to tangle the wires when tightening the actuator as the spinning motion easily frays wires. Different brand actuators seem to have provision for different size wrenches, too. Also I found it easier to smoke while working on the actuator instead and have a beer later.

    Thank you for the nice writeup. I find it really hard to even get out of the driveway without functioning 4x4 in the wintertime. This guide will help when the actuator inevitably fails again.
  5. Jay P

    Jay P Newbie

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    Jun 2, 2017
    Dallas Tx
    Did this method on my 88 GMC K1500. It definitely works. I have 4LO but I don't have 4HI. I think it's a problem with my transfer case. Every time I shift into 4HI it pops out. Anyone have this problem or the solution, gladly appreciated.

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