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1988 chevy k3500 4wheel not working

Discussion in 'Chevy Trucks' started by terrapro, Nov 10, 2011.

  1. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,873

    I just bought a 1988 chevy k3500 today. Yesterday I test drove it and the 4wheel worked fine, today the guy dropped it off and we were going through everything and the 4wheel won't engage now. When you put it in 4high you can feel the gears change and the torque increase but the front drive won't work.

    I dug threw old threads and the problems and it seems it is either the actuator or the switch, how do I know which one it is? Or could it be something else?
     
  2. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Check for voltage at the actuator when the key is on and the case is in four wheel. There is a fuse for the actuator, check that first.
     
  3. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,873

    The actuator is on the passenger side facing towards that wheel correct? Surprisingly I have had 4 of these trucks and never had a problem.
     
  4. Chrisxl64

    Chrisxl64 Senior Member
    from CT
    Messages: 574

    if you feel the transfer case engage, and spin up,,,could it be an auto lock hub problem?
     
  5. Chrisxl64

    Chrisxl64 Senior Member
    from CT
    Messages: 574

    wow,,,feel like a moron rolled down didnt see anyone had already replied about actuator,lol.
     
  6. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,873

    No, we do not feel the case spin up. I can feel the transfer case engage while moving the lever with someone under and someone over. So I assume the transfer case is engaging but the front wheels will not turn...but if i put it in 4low I can feel the torque almost double, it will bend the truck almost...4:56 gear.
     
  7. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,873

    No I feel like a moron! I own three of these trucks and don't know where the actuator is, honestly never had a problem until now.
     
  8. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Correct. Looks like this.

    CAD.jpg

    CAD.jpg
     
  9. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,873

    thanks 2COR! From what I have found they are around $80?
     
    Last edited: Nov 11, 2011
  10. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,873

    Nope not it. So next on the list is the transfer case switch. Local store couldn't get it for me until tomorrow but we havn't tested it yet anyway.

    BUT in the process of testing for the 4wheel we managed to blow the wheel cylinder in back. I was going to rebuild the back brakes anyway, better sooner than later I guess.
     
  11. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    That's about the right price. Even though it is currently working, you might consider a couple options. First is to simply put a spacer in axle housing then screw the actuator in. A 3/8 drive socket, about 7/8, works well. A lug nut will work too. The big advantage to the spacer is that you will have instant 4wd when you pull back on the lever. The disadvantage is a slight impact to fuel economy. On a one ton with 4.56 gears it's not going to make much difference.

    This is the other/best option..

    http://www.4x4posi-lok.com/
     
  12. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,873

    Well I have now replaced the acuator and the TC switch and patched some broken wiring but still won't work. My tester is on the fritz so I can't check for voltage yet but I have to assume I have more broken wiring somewhere because I can't think what else it could be.
     
  13. Chrisxl64

    Chrisxl64 Senior Member
    from CT
    Messages: 574

    Cor Im missing the concept here,,,can you re-explain?
     
  14. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    Two things happen when four wheel drive is engaged: The transfer case is shifted and the front differential locks into the driveshaft via the electric actuator mentioned above. If you take the actuator out and put your finger in there, there is a spring loaded plate the the actuator pushes on to do this. What 2COR is saying is to put a spacer in the tube that always keeps that spring plate compressed keeping it locked in all the time so the only thing left to shift to get 4*4 is the T-case.

    This is how ive engaged the 4*4 on my 97 for the last couple years as I cannot for the life of me figure out why I can't get power to work in the plug for the actuator (mine is the new style though). I use a lug nut with a valve spring on it ;-)

    The other option that ive done before is to take that older style Thermal actuator like 2COR posted a picture of above and wire it into its own switch on the dash. That way you eliminate the possibility of the switch on the T-case failing to send the signal to the front diff actuator on its own.

    OR you can get a GM update kit that converts your old style thermal wiring to the new style actuator which is a much faster and reliable system. But if your T-case actuator switch is faulty that would still have to be replaced to be able to do that conversion.
     
  15. Plowtoy

    Plowtoy Senior Member
    Messages: 929

    This is the best way to FIX your problem IMO. I did a bunch of these in the late 90s when i was working at the dealership. Its a pretty simple upgrade and not real expensive
     
  16. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,873

    Unfortunately I have already dropped $100 on trying to fix the problem so I am kinda commited now. I am pretty sure it is a wiring problem, what else could there be?

    Anyone know anything about these 88 K3500 camper packages? I just put about 25 miles on it around town and it is a torque monster. Its not the power from the motor but its got to be the gearing. Did they put a different build on the trans because the shift points seem lower and of course being a 3 speed with these gears in the rearend it doesn't like to go faster than 45mph without the motor feeling stressed.
     
    Last edited: Nov 14, 2011
  17. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Does the truck have a tach?
     
  18. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,873

    No tach. It shifts with light throttle from 1-2 at 10-12mph and 2-3 at 22-25mph, heavier maybe almost half throttle 1-2 18mph and 2-3 at around 30mph...seems alittle low to me. But I think the speedo is off as at 45 on the speedo people are usaully just barely passing me in a 55mph zone.
     
  19. Chrisxl64

    Chrisxl64 Senior Member
    from CT
    Messages: 574

    If your lucky enough to have your build codes, that will tell you what rear gears you have.

    Codes for rear ends:
    G75 3.70 rear

    G76 3.36 rear axle ratio

    G80 Positraction rear

    G82 4.56 Rear axle

    G84 4.10 Rear axle

    HO5 3.73 Rear Axle


    If not,,,you could always pop the cover, and check the gears themselves. Never hurts to change diff fluid anyhow.
     
    Last edited: Nov 15, 2011