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4 WD Problem

Discussion in 'Truck & Equipment Repair' started by B&E snowplowing, Jan 20, 2010.

  1. B&E snowplowing

    B&E snowplowing Senior Member
    Messages: 159

    I have a 1995 GMC 2500, went to put it into 4wd to clean up my driveway last night, the indicator light came on, and when I went to go it made a terrible grinding noise from the front end. When I put it in reverse I SLOWLY stepped on the gas and didn't hear the noise, and the 4wd was engaged. After that everytime I stepped on the gas either slowly or not the noise was there. Not to sure of the problem, but I am leaning towards the 4wd actuator...Anyone have any other ideas.
    Thanks
    Brian
     
  2. clark lawn

    clark lawn PlowSite.com Addict
    from NE ohio
    Messages: 1,233

    actuator froze up, very commen problem
     
  3. B&E snowplowing

    B&E snowplowing Senior Member
    Messages: 159

    Thanks for taking the time to reply.....I will take a look at that, heat it up, and if that dosen't work go out and get a new one.
     
  4. chris694205

    chris694205 Senior Member
    Messages: 175

    you can take that actuator out of the front diff and have someone put it in 4 wheel while your under it and will be able to see it move... if its not that there is a small actuator on top of the transfer case that is about 30 bucks.. i believe it is a sensor that tells the front actuator when 4x4 is engaged
     
  5. plowking15

    plowking15 Member
    Messages: 91

    I believe the actuator has a gas inside that expands to engage/disengage the front axle. The actuator move a shifting fork that moves the axle,if axle is partly engaged,it will grind or sound like a gunshot if you are putting power to it before it is locked. I had the axle,shifting fork,actuator on mine replaced when I first bought it. The stuff was hammered before I got it. I always wait a second and throttle easily until I know it is engaged to try and prevent damage. Do the same on the newer truck.My newer truck is work truck edition,it has transfer case lever, I'm not partial to pusk button 4WD. plowking
     
    Last edited: Jan 24, 2010
  6. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Plowking's analysis is the most accurate.

    The problem with taking it out and seeing if it works, is that it will fool you. When it's not bolted to 50 lbs of cast iron, and not pushing against the spring, it will heat up and move quickly.

    But, your symptoms sound very typical of an actuator getting tired. And pulling it out and putting the truck in 4wd (with the key on) is the quickest and easiest way to confirm your wiring and transfer case switch are all working.

    Cheapest, and most reliable way to finish the plowing season is this. Pull the actuator, place a lug nut in the actuator cavity, and put the actuator back in. This will keep the front axle engaged all the time, and you will never wait for 4wd again. That's the way I have both of my trucks setup right now. Hit the button, instant traction.

    Come spring, put in one of these.

    http://www.4x4posi-lok.com/app_chevy-k.html
     
  7. B&E snowplowing

    B&E snowplowing Senior Member
    Messages: 159

    Thanks for the replys, I purchased a new actuator $199.95 and installed it and I still get the same grinding noise, only when in 4wd. I suppose the front diff is garbage and now going to have to find one somewhere and replace it. Was kinda hoping it was going to be an easy fix. Guess not.

    How common is it that the fork, and spring that the actuator presses against breaks. Does anyone know if you can replace those easily and cheeper then getting a new diff, and if so can you pick the parts up at a local parts store.

    If it wasn't that I have spent a TON of money on this truck, I would be sending it to truck heaven, but I'm in pretty deep so I might as well keep going. New Engine, Trans, Fuel Lines, Exhaust from heads back, Gas tank, fuel pump sending unit just to mention a few. And the body is still in really good shape.

    Thanks for your help
    Brian
     
  8. chris694205

    chris694205 Senior Member
    Messages: 175

    i have replaced a ton of those front diffs... sometimes for grinding like you say and sometimes for just not engaging in 4X4... we can pick up a used one at our local junk yard for 150-200 bucks and its pretty easy to put them in.. just make sure you get a low mileage one if you go used
     
  9. theplowmeister

    theplowmeister 2000 Club Member
    from MA
    Messages: 2,551

    When you replace parts willy nilly it gets expensive. the collar and shaft can wear (you know from all the grinding it did) you could check and see how far the actuator moves, then see if the collar will engage the splines enough to be a solid connection, and if the collar and shaft have excessive wear.

    Of course you might want to find the problem before you replace the diff. you could, I don't know, TAKE THE COVER OF THE DIFF AND LOOK:dizzy: If its bad there will be all kinds of pieces and filings, broken teeth... in the diff. Its possible that the the splines on the shaft and hub halve sheared (I've never seen that, but you could be the first.)

    LOOK and CHECK before replacing. a simple check would have been how far the actuator moves. Can you, by hand, stop it from moving?.

    I read all the time where people ask what can it be, and replace the most popular fix ONLY to NOT fix the problem. A better question (although it takes work) is HOW DO I FIND WHAT IS MAKING THE NOISE.


    Sorry for the rant :rolleyes:
     
  10. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Did you confirm you are getting power to the actuator? You could have a blown fuse, or bad switch on the transfer case.
     
  11. theplowmeister

    theplowmeister 2000 Club Member
    from MA
    Messages: 2,551

    If he is getting a grinding noise from the front, how would a blown fuse (that would prevent the actuator from working) cause that?
     
  12. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Good point!

    My bad:blush2: