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1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next?

This is a discussion on 1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next? within the Technical / Maintenance forums, part of the General Discussion category; 1988 chevy 4x4.. Fresh tranny rebuild.. Just last week got the front driveshaft back in it. 4x4 doesnt work.. Checked ...

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    Exclamation 1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next?


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    1988 chevy 4x4.. Fresh tranny rebuild.. Just last week got the front driveshaft back in it.

    4x4 doesnt work..

    Checked

    Alll connections on the front driveshaft.. All good!
    Checked voltage at the Actuator( 3 wires, so i want sure which was which, but most i got with truck running and it in 4hi was 2.3 volts.. )

    checked connections at transfer case.. All good.

    I have no clue which fuse controls the 4x4, but i didnt see any burnt ones.

    When i put the FLOOR shift into 4hi nothing happens( front driveshaft spins when truck is off the ground all the way around, but wheels dont.)

    when i put it into 4lo it cluncks( as it did when it was working) but no lights. The t-case drops into the " low gear" and it lunges without giving it gas( as it did before)


    Any ideas??

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    Re: 1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next?

    Nobody has any ideas?

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    Re: 1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next?

    Normally, the problem in those trucks is the actuator.
    The replacement wiring harness usually only comes with a replacement actuator that is different from the orriginal.
    I will send a couple links about some stuff I have found on line, but have never personally tried. They sound like a good idea, but I have stayed stock for years, and am still running about six trucks in my fleet with the old style.

    I assume you checked your fuse again after it quit again?

    Here is how the power goes.
    When the ignition switch is on, there is power to the 4X4 fuse. Power goes first to a switch on top of the transfer case. That switch is just about below the passengers seat, and if the truck has seen some rough 4X4'ing, I have seen the cross member under the transmission bent, and that switch kinda jammed up against the floor.

    So..with power going to that switch, you shift the transfer case into four wheel drive. That closes that little switch, and sends power to the front axle actuator, and to the switch on the front differential for the 4X4 light. As the actuator expands, and engages the right front axle shaft coupler, it closes the light switch, and illuminates the 4X4 light.
    I would check those switches, and especially their wires, and make sure one of them isn't shorted to ground.

    Here are those links, and although they are very interesting, a couple statements are not 100 % accurate. But all in all, some good information.

    http://www.4x4posi-lok.com/PDFs/troubleshootguide.pdf

    http://offroadltd.com/Merchant2/merc...e=ORL&Product_...

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

    http://www.pirate4x4.com/welcome1.html

    http://www.pirate4x4.com/tech/billav...aft/index.html

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    Re: 1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next?

    Which fuse is the 4x4? There isnt one marked in the fusebod on the driver dash>>>

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    Large Marge sent me SUBURBIAN's Avatar
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    Re: 1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next?

    Have you had the actuator out and in your hand? Have you inspected it? When you have it unplugged and out, where is the actuating button parked? All the way in? All the way out? In the middle somewhere?

    Once it is out, you can shine a light in the diff and see what it actuates. Some guys replace electric actuators with cables. All the actuator does is push a rod, that pushes collars together to lock the fronts together and to the driveshaft. The rod that it actuates against is spring loaded to return to 2wd. If you spin one front wheel in 2wd,with both fronts jacked up, the other one stays still. Stick your finger in there and see if you can push the rod in... Push it in and then spin the pass front wheel. Watch the driver front wheel, if the 4wd engaged, the driver front will spin too... Then, you know it is the actuator. Ask me how I know.
    Last edited by SUBURBIAN; 09-16-2010 at 09:59 PM.
    1996 GMC K1500 SUBURBAN SLE
    355" L31 : DELPHI MPFI : 2.25" THRUSH DUALS : RCX SUSPENSION LIFT : RCX STEERING STABILIZER : RCX 2.2 SHOCKS : MOOG EVERYTHING : SMITTYBILT NERF BARS : OPEN GT4'S : DICK CEPEK DC2'S : 295/65/18 DURATRACS

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    Re: 1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next?

    Havent pulled the actuator out.. just unplugged it and couldnt get voltage at the input wires.. It worked fine before the tranny rebuild..... i was hoping it was a fuse or something.. Im trying to sell it and dont want to sink any more money in it..

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    Re: 1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next?

    I had an 89 I bought new. I had a couple friends that had the actuator crap out on them. One was five miles from the nearest paved road on top of a mountain. He was lucky there were two trucks in the group. He had to be pulled up a couple hills to get out. I decided to find out how the axle locked in. I pulled the actuator, plugged the wire back in and watched it stroke. I built a spacer to insert in the hole and screwed the actuator back in without the wires connected. Locked the front just fine. I built a lot of those and gave to my friends. I carried that spacer in three other trucks and never had the need to use it. I still have it in my tool box. If anyone wants to make one I would be glad to post the dimensions and explain how to get it in to stay while inserting the actuator. Later! Frank

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    Large Marge sent me SUBURBIAN's Avatar
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    Re: 1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next?

    A broken actuator and a deep socket of the correct dimension will also lock a diff into 4wd.
    1996 GMC K1500 SUBURBAN SLE
    355" L31 : DELPHI MPFI : 2.25" THRUSH DUALS : RCX SUSPENSION LIFT : RCX STEERING STABILIZER : RCX 2.2 SHOCKS : MOOG EVERYTHING : SMITTYBILT NERF BARS : OPEN GT4'S : DICK CEPEK DC2'S : 295/65/18 DURATRACS

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    Re: 1988 Chevy silverado 4x4 help. Ive already trouble shot.. what next?

    1) Make sure the switch is plugged in on the transfer case. When I replaced my trans, I did not get it seated correctly (but clipped in place) and it left me out in the middle of the woods with 12+ inches of fresh snow. Make sure the wires didn't get pinched/broken in the trans rebuild process.
    2) make sure there is power going in the above mentioned switch.
    3) ensure the above mentioned switch is closing and power is leaving said switch.

 

 

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