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99' 1500 4wd transfer case help

Discussion in 'Chevy Trucks' started by crazywelder72, Mar 24, 2010.

  1. crazywelder72

    crazywelder72 Junior Member
    Messages: 26

    my 4wd just starting screwing up on my 99 Silverado at 99,980. im the original owner and have had almost no problems with my truck other than normal wear and tear (except for my annoying abs light that comes on for no reason) i am quite savvy with troubleshooting issues however i don't know if its the encoder on the transfer case or something more at the computer level. while at a red light in 2wd my service 4wd lamp came on and the truck went into 4wd and all the 4wd led's went out and i had no button operation.

    99% of google results say its the button assembly and swapping or re-soldering will fix it. its not it. i have disassembled, inspected, reassembled and swapped with a loner switch form my wife's 2002 Tahoe ( i love that truck) and this didn't do anything other than rule that out. Typically the lights on the 4wd buttons flash once quickly then flash a second time for a longer duration before going into the mode it is in. now mine only do the initial quick flash. somehow i got the truck into 2wd and proceeded to pull the fuse on the left of the dash to prevent it from inadvertently popping back into 4wd

    I replaced the actuator on the front differential and this didn't do it either. however upon testing out the buttons after installing the actuator and the fuse the lights and actuators started to work but weren't responding like normal. when i would shut off the truck and start it it would default to 4LOW but would change out at the press of the button. after some more attempts with the key on/off pulling the fuse and trying to somehow "flash" it back to a normal behavior i finally got it so at least when the key went on it came back to 2wd.

    after a few more button presses it once again went into 4Hi and the lights went out again. now its stuck and i cant get it back to 2wd as the lights are behaving as stated earlier (basically dead except for initial flash). i dont want to throw the money at the encoder on the transfercase if its something else.

    any ideas??? anyone.....anyone.....
  2. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    First check all the wires down by the axle and make sure there arent any corroded or got a bad spot in them, and also the ones going into the encoder motor on the t case. Since you did the buttons and the front diff actuator, then I am willing to be hands down encoder motor.
  3. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    You say the service 4WD light on? If so, have you pulled the codes? Check for CO327... Encoder motor error. If that code is present, you most likely need a position sensor.

    You can disassemble the encoder motor and replace the position sensor. Nine times out of ten, that's all that's wrong with them... no need to replace the whole motor.
  4. crazywelder72

    crazywelder72 Junior Member
    Messages: 26

    all i have is a obd2 reader and that wont read the 4wd codes. i didnt know that the encoder is serviceable. thats cool but i need to minimize down time. i will try to find some info on how to service it and the replacement part. at least thats cheaper than swapping the whole encoder.