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4 wheel drive won't disengage

Discussion in 'Chevy Trucks' started by flykelley, Feb 23, 2013.

  1. flykelley

    flykelley 2000 Club Member
    Messages: 2,127

    Hi Guys
    Been having a hard time getting the 4 wheel to engage, sometimes I need to come almost to a stop. Got it to engage for the storm friday, now it won't come out of 4 wheel drive. I replaced the actuator on the front axle, that didn't change anything. Push buttons just blink then it stays in 4 wheel drive. Suggestion? Its a Chevy 2005 2500HD.

  2. Newdude

    Newdude Senior Member
    Messages: 889

    Shift module or encoder motor?
  3. gc3

    gc3 Senior Member
    Messages: 713

    Mine did that before. I had to replace the 4x4 control pad. It was malfunctioning. It was expensive. Sometimes I could turn the ignition off and on and sometimes it would reset something and then it would work enough to shift in or out of 4x4.
  4. racer47

    racer47 Senior Member
    Messages: 381

    :mechanic:i have 98 did same thing i installed new actuator , didnt fix. replaced switch didnt fix.. replaced encoder moter done. switch was good .not sure about actuator it was encoder moter. for sure on mine . but it has did it again 1 time sence replaceing everything .connection on actuator dirty cleaned put on dielectrical greese fixed problem... ((( check your connections first)))) a good :mechanic: can test to make sure your getting 12 volts to both places to determan whats bad.. but i dont think the switch inside cab is bad. my bet would be encoder moter or bad connection i had to drive my truck throught high water, thats what did end encoder moter.. 2- 1/2 ft or higher water . wasnt by choice had no other options long story . good luck ussmileyflag:waving:
    Last edited: Feb 23, 2013
  5. kimber750

    kimber750 PlowSite Veteran
    Messages: 4,676

    My blazer does this about once a year. For me disconnecting the battery for a minute seems to fix it. Haven't looked any further into the problem.
  6. BigLou80

    BigLou80 Senior Member
    Messages: 558

    mine did that. It was the encoder motor.
  7. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,391

    take off the motor on the t-case,,,,have someone turn on the 4x4 hi, lo, 2wd and see if the motor moves.
  8. PowersTree

    PowersTree Senior Member
    Messages: 586


    I'm 99% sure it is the motor on the transfer case.

    When the lights on the dash flash, its the motor.
  9. Eggie329

    Eggie329 Senior Member
    Messages: 123

    Mine has pulled this on me once in a while. I slow it down to about 5 MPH and just keep pressing 2 WD. Eventually it will just drop out of 4 WD and its fine! Everything is less than a year old, axle actuator, encoder motor, transfer case, control module and switches and mine has done this every now and then since I replaced everything!
  10. 32vld

    32vld Senior Member
    from LI, NY
    Messages: 622

    I have a 2001 GMC suburban. I have found that going in and out of 2hi and 4hi will work best when foot of the gas and coasting under 10 mph with the transmission in neutral. Yes it will go in and out of 2hi and 4hi in gear but it is faster and smoother in neutral.

    As to going in and out of 4lo it works best coasting at 1 mph foot off gas and brake, trans in neutral.
    Last edited: Feb 26, 2013
  11. My 2002 2500HD was the encoder motor on the TCase when the lights were flashing on the switch.
  12. royallawn

    royallawn Senior Member
    from kansas
    Messages: 156

    same problem on my 99, will check the encoder motor. how much is the motor?
  13. PowersTree

    PowersTree Senior Member
    Messages: 586

    Unfortunately, it's the most expensive part of the system. Not sure what they're going for now, but it was about $400 when I needed one.
  14. buddymanzpop

    buddymanzpop Senior Member
    Messages: 603

    You may not have to replace the entire encoder motor unit, there is a serviceable part inside the encoder motor assembley, it is the encoder motor sensor, it senses what position the shift gear in the encoder motor assembly is in. Rockauto sells the part for around 55 bucks + shipping, auto parts stores are $80 to $90. I just replaced the sensor in my 2006. I had the symptoms of the red neutral light illuminated on the 4wd selector switch and when I tried to get the 4wd to engage the light on the button would just flash and not engage, soon after I got the service 4wd message and then the 4wd switch went completely out (no lights at all). Swapped out the sensor and all is back to normal. Also check your grounds on the frame rail below the drivers door towards the front near the cab mount, dc them and clean everything with a wizzer wheel, reassemble and paint or undercoat, if your lucky it could be that easy (although it's never the easy fix). Electronic 4wd shift components are, selector switch, transfer case control module and encoder motor. If you decide to go after the EM sensor and need any tips let me know. The sensor I mentioned is also referred to as an "Encoder Ring".
    Last edited: Mar 24, 2013
  15. flykelley

    flykelley 2000 Club Member
    Messages: 2,127

    Hi Guys
    It was the encoder motor, I just swapped it out and life is good.