1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

Odd 4WD Problem

Discussion in 'Chevy Trucks' started by DeereFarmer, Jan 19, 2010.

  1. DeereFarmer

    DeereFarmer PlowSite Veteran
    Messages: 3,296

    I've known for a while now that I have a bad CV joint on my truck. I just wanted to make it through our latest storm before I got it in, which it did make it through. Now when I try to engage the 4WD button (not a lever shift... man I miss those) the 4WD won't engage. Is this a seperate problem or could this be linked to the CV joint? I am pretty sure it's not related, but though it'd be worth asking someone who might know more than me!:D
  2. Novadiecast

    Novadiecast Senior Member
    Messages: 194

    I think you are on the right track, but I would wait for more knowledgeable to answer.
  3. DeereFarmer

    DeereFarmer PlowSite Veteran
    Messages: 3,296

    Whew, atleast I'm not totally out of my mind! I press the 4WD high button, it blinks a few times, and then clicks back to 2WD.
  4. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    Nope it could be the front diff actuator or the T case encoder motor going to shyt. I think mine has a cv on the way out, but the 4x4 still works with no issue. And mine is push button as well. Get under it and check around the T case and make sure there is nothing against the encoder motor (on front of case, right above the skid plate) Check the fuses for the 4wd as well, as there is a fuse under the hood for the shifting. If you do a lil searching B&B has responded to issues with the push button t cases and the problems you are having
  5. andcon83

    andcon83 Senior Member
    Messages: 388

    If you need an encoder motor, I have one that I bought for my 2001 hd. I never put it on. I traded the truck. Let me know if it is something you need. I changed the 4wd button and it didn't make a difference on mine. The 4wd light would come on and it wouldn't shift. Turn the key on and off, and sometimes when you turned it on it would work great. Or if I drove down the road a few miles it would work fine. When it was warmed up, it shifted great.
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    When it blinks the requested function but doesn't complete the shift, and then goes back to the previous position it's either the encoder motor not working or the front axle actuator thats not shifting. Either due to the axle actuator itself being defective, or the wiring to it. There's an electrical connector plug about 8" from the actuator that can be damaged from road debris/plowing and ice buildup so be sure to check there first. You can also check for the correct signals there with a test light so make sure the commands are being sent. Just takes a little time and knowledge to do so.

    If the encoder (on the T-case) is attempting to shift but there's an issue there you'll normally still hear the familiar "clunk" as it shifts...can you hear it?

    A bad CV has nothing to do with the 4WD not attempting to be electrically engaged btw.
  7. DeereFarmer

    DeereFarmer PlowSite Veteran
    Messages: 3,296

    Thanks guys. I do not hear the familiar clunk B&B. So we think it may be the encoder?
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Yes, that or the switch panel as yours is an '02 and they were very susceptible to the switch panels dying. No way to tell which one of those two is the issue though without a good scanner. Unless you're just going to throw parts at it which I do not recommend. If you can't get access to a good scanner pay the money and have it scanned for you. With a scanner not only can you check for any 4WD specific codes but you can also view the commands sent to see if the switches are actually sending the commands and the encoder is actually receiving them. Knowing this info, its an easy fix then.
  9. DeereFarmer

    DeereFarmer PlowSite Veteran
    Messages: 3,296

    B&B you are the man sir. I have a buddy that'll scan it for me at his shop on Monday and we'll see what the result is. Thanks as usual.
  10. DeereFarmer

    DeereFarmer PlowSite Veteran
    Messages: 3,296

    It turned out that the whole encoder motor was junk. The bearing on the inside was corroded really bad. Luckily found and aftermarket one for about 1/3 less than what GM wanted for one.
  11. damian

    damian Senior Member
    Messages: 330

    you cant guess with these things,its way too expensive.plug into it with a scan tool,find someone with a tech 2,if it is the encoder and it could be it will show up on the scan tool.look at the data page for the transfer case and if the encoder is screwing up you will see the data for transfer case gear position fluctuate from low to high to 2wd and 4wd.good luck.