91' Silvy - lost 4wd?

Discussion in 'GM Powertrain' started by bigburb, Nov 8, 2009.

  1. bigburb

    bigburb Rockstar ROTM Winner 100 Posts

    Hey guys, I got a new problem for y'all:

    I was screwin around in a big muddy ditch with pretty steeps sides and some slick mud and like 2" of water in the bottom. I went through it forwards, but couldn't make it up the dry walls of it with mud covered A/T's. So I put it in reverse, and couldn't make it up the other side, and tried to come forward again, to no avail. So i was basically stopped in the middle (which was strange, because it was just slick mud, only sunk about an inch). Then, my friend, who was sitting in a different truck, told me my front wheels weren't spinning (keep in mind up until this point, the 4wd was engaged and spinning). I looked down, and the shifter was still in 4, but the indicator light was off and obviously not in 4wd anymore.

    Anyways, my friend pulled me back onto the street and I started testing it. There's no strange noises, clunks, clangs, or anything of the sort. I simply just don't have 4wd anymore. The 4wd lever goes into 4lo, N, 2hi, and 4hi seamlessly like it should.

    I was hoping it's just a sensor or an actuator or something, but I just got this truck about 10 days ago and this has me stumped...

    NEW UPDATE: Ok, I was looking under the truck and the sensors, wires, and all that jazz and decided to take a look at the fuseboard. Locate and pop out the 4wd fuse, and it's fried. Pop in a new fuse, slide the lever up to 4lo, and immediately saw a bright blue glow from fuse roasting. The fuseboard calls for a 25A fuse, which is what was in it and is what I put back into it. Any suggestions?
    Last edited: Nov 8, 2009
  2. KidHauler

    KidHauler Epic Member 5+ Years 500 Posts

    Aren't new toys fun?

    I think you're on the right track - crawl underneath and look for something unplugged. If either the front diff or t-case plugs have come loose, it may have opened the circuit, causing the light, and the 4x4 to go out.

    Good luck,
  3. bigburb

    bigburb Rockstar ROTM Winner 100 Posts

    Man, that would be cool if it was something as simple as that. It's dark out right now so that will have to wait till tomorrow.
  4. unplugged

    unplugged Epic Member 5+ Years 1000 Posts

    If not a short, it is probably the actuator. Not a big deal. Easy to replace. I bought an original style actuator from NAPA for about $80. GM will only sell you the new actuator and harness for $$$$. The thermal actuators had problems and later models changed to a different part. To use the newer actuator the harness has to be replaced so the price is closer to $300. I figured if the original lasted 200k then I didn't see anything wrong with saving a few bucks and sticking with the original design actuator.
  5. bigburb

    bigburb Rockstar ROTM Winner 100 Posts

    Yeah that would be nice. But with the instant-fuse blowing I just discovered, it has me wondering. Could a bad actuator cause this? Or are they mechanical? Any other ideas what might cause the 4WD fude to blow as soon as I move the lever into 4hi or 4lo?
  6. bigburb

    bigburb Rockstar ROTM Winner 100 Posts

    Any suggestions? I need to get this fixed soon because Colorado is supposedley going to have a pretty nasty winter... We already had 14" almost 2 weeks ago and I'm going to need it when we get more snow here.

    I know it's an electrical problem now. You can read about what happened in the "EDIT" I put in my first post.

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