4WD issue

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by SeaSalty, Jun 25, 2013.

  1. SeaSalty

    SeaSalty New Member

    I've been having a 4WD issue for the past year, 4WD switch lights aren't even on, Service 4WD message stopped showing after a while. I finally managed to change out the transfer case encoder motor today, and now my 06 silverado will not even go into drive/reverse. The switch lights still aren't on and I can hear a clicking noise from the new motor whenever putting it into reverse, neutral, drive, and it makes a grinding noise if you try to put it back into park. So, now I turn off the truck before putting it into park.

    The way I installed was taking out the front driveshaft, taking out the old encoder motor, and gear orientation from the transfer case was different from the new encoder motor so using pliers I change the gear into proper orientation, so the new motor would fit, plugged everything back together, and now I can't even drive.

    Any ideas?
  2. Family Force 6

    Family Force 6 Rockstar 100 Posts

    I remember reading somewhere that you're supposed to have the transfer case in a particular mode (I thought 2WD) before removing to make sure that the new encoder motor would be lined up properly. However, it seems to me that even if the encoder motor wasn't engaging properly that you should be able to move in 2wd, but I'm not an expert in transfer cases.
    I know my transfer case started making grinding noises even in park right before it completely self-destructed. So it could be that it's more than just an encoder motor issue. I hope for your sake that it's not.
  3. j cat

    j cat Epic Member 5+ Years 1000 Posts

    nI would check all the fuses since the dash switch lights are inop. the encoders come in the neutral position. so if it was possible you should have placed it in the 4wd neutral . moving the fork for the new encoder to lock in is what is done if you cannot get to the neutral position.

    with the lights not working I would not say that is the reason to replace the encoder . wiring to these is very fragile. wiring and the encoder feedback position sensors also. many times the transfercase is binding because the fluid is black or very gray. with this the movement can cause fuses to blow /motor failure of the encoder.
  4. SeaSalty

    SeaSalty New Member

    Thank you for the reply

    I forgot to mention that the previous encoder motor wiring harness was shredded up from I presume constantly hitting the front driveshaft as it spins which led to my initial 4wd problem. I spoke to some friends and decided I would try to replace the push-button dash switch hoping that maybe the switch went out as well. If that doesn't work then I am completely stumped.


    Replace push-button dash switch and new switch lights still do not illuminate.
    When engine is running the motor is still making the clicking noise.

    I'm thinking of a possibility that gears weren't aligned correctly.
    Last edited: Jun 25, 2013
  5. j cat

    j cat Epic Member 5+ Years 1000 Posts

    the wiring is a problem with these when people handle these wires with lack of proper care.

    wiring most times fails because work was done and these wires also did not get properly set back in the OEM holders/position.

    you may have the transfercase fork backwards. never ever try to rotate the encoder motor as this is in the locked mode. with power to the unlock solenoid then the motor rotates.

    some have had the wire to the solenoid break , then the encoder obviously will not rotate.

    these wires are very small and very easy to break. check the fuses again with a meter.
  6. SeaSalty

    SeaSalty New Member

    I checked the fuses today with a testlight and they were good. Doing a bit more research I believe the TC Control Module isn't sending/receiving a signal from the encoder motor which may be why my push-button lights aren't lit and why the encoder motor can't shift into a gear. I've pulled out the module and I'll try and get a new one tomorrow.

    Also, I checked the wiring harnesses and can't find anymore damage. I'm not totally sure what you mean by TC fork being backwards? I rotated with transfer case into neutral with pliers, so the new motor could fit as I did read beforehand to never rotate the encoder motor.


    Replace TC Control Module and still nothing, went back underneath and took off encoder motor again. Really stumped at this point, I'm trying to check all the harnesses and grounds.


    Found TREC fuse blown and replaced with 30AMP fuse. Still in same position nothing has changed.
    Last edited: Jun 27, 2013
  7. j cat

    j cat Epic Member 5+ Years 1000 Posts

    the use of a test light is not recommended. use a VOM to check fuses and circuits.

    it is very rare to have the control module fail.

    what is the color of the transfercase fluid ?

    check the ATC fuse with a meter. also at the traction control module make sure the black wire goes to ground. check that the light green/black wire has 8 volts DC on it using the black wire as the return with a voltmeter.
    Last edited: Jun 29, 2013
  8. SeaSalty

    SeaSalty New Member

    I'm not sure if I did it right. The TCase fluid is brownish-black. I checked the TREC fuse which I think is the ATC fuse with a multimeter and was reading 15V DC on each side. I went underneath and found where the harness hooks up to the encoder motor and found a light green/black stripe wire on the harness and using the positive lead I had it held slightly above where the male pin would go and had the black lead pressed against the lower front body ground while the engine was running and got a bunch of mixed unstable numbers it ended around 28 V. I'm pretty sure I did it wrong. I'm using a Innova multimeter with the setting on DCV.
  9. j cat

    j cat Epic Member 5+ Years 1000 Posts

    now the reason I asked about the fluid color is it should be blue. when the fluid requires replacement it will turn a grayish blue color. this is when to replace fluid. this is usually 40,ooo miles of normal not so much 4WD operation. with 4wd operation towing/plowing this is done every year.

    since the fluid is brown/black this is usually the transfercase is damaged. the encoder motor wil have a hard time operating with the fluid damaged/contaminated. you can try a fluid change to see if things improve.

    the wiring must be working / repaired.

    I have also found that under the fuse box[under the hood] that the rodents chew up these wires/connectors located there. removal of the fuse box [lifting off the fender] and under the fuse sockets is where you will see many wires connectors. make sure none are chewed up or with no insulation. this I have found and is problem with the animals.

    - - - Updated - - -

    The small wires are the feedback wires which tell the controller where the encoder motor position is. the green/black wire should be the 8volt dc which feeds the encoder position sensors.

    obviously all these wires and fuses along with the transfer case to operate is required for this to all work.

    I would place the meter to a 9 volt battery and see what it reads to be sure its working ok. also make sure the internal meter batteries are good or your readings will not be correct.
  10. SeaSalty

    SeaSalty New Member

    The fluid was more of a greenish-black, but I went ahead and changed it with Auto Trak II, I checked the fuse box and it looks like everything is fine nothing, but just casual dust.

    I believe the problem is the TC Control Module isn't getting power to it, so I have been trying to figure out where the wires go so I can trace them back for damage, but no luck on my end. I've also come to realize that it isn't the encoder motor making the clicking noise, but is instead the transmission.

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