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Thread: Automatic 4WD does not 'turn on'???

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  1. #1
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    Unhappy Automatic 4WD does not 'turn on'???

    Hey!
    This is my first post on TVT! I'm excited to learn, and hopefully to gain some experience and share too.

    ANYHOW...

    I have a new-to-me '87 4WD with the push-button 4wd with so-called automatic hubs. Tonight there was a wicked snowstorm with some mean ass drifts. So I stopped, and pressed the 4WD button, and then proceeded to drive. A few minutes later I encountered a slick hill, and ONLY THE REAR WHEELS WERE SPINNING. I am 99% sure that no 'power' was reaching the front wheels. They weren't even trying to spin.

    it was as if I just had a rear wheel drive van. no offense to you 2wd van folks, but I was bummed out. i was also stuck. some dude in a ford excretion was really nice and pulled my van up the hill and then a few blocks to my driveway. i am super grateful that a stranger hooked it up, but I just got a 4WD van so that I could be the man and I was left feeling mighty lame.

    what are my first steps in diagnosing the 'problem'? I want to make the 4WD operable. I want to have some clue as to what the 'real' problem is before bringing this to a mechanic. is there some way that I can determine whether the problem is the hubs or the...???

    my lady already thought i was nuts to go dump some $$$ on some old van. i told her it was cool because it was 4wd, and that i'd be taking her places she'd never imagined. i need this fixed before she finds out it doesn't even go into 4wd!

    thanks van techs!!!

  2. #2
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    Re: Automatic 4WD does not 'turn on'???

    Welcome to the site!

    Living in central Texas I can appreciate a good northern snow story. Thank you for reminding me of my northern days.

    I don't have a 4wd - I wish I did, but then again, it would just be another thing to fix.

    However, I do know that the manual hubs are the preferred 4wd hubs to have - probably because of problems like you are experiencing. I believe its pretty easy to swap out the auto for the manuals.

    It's easy to get frustrated with the search feature here & on TVP where they make you wait a minute to click through the next page of results. But both sites hold a fountain of information though & I find it much more efficient to search these two sites with Google using the site command.

    4wd auto not working site:toyotavanpeople.com
    auto hub problem site:toyotavantech.com

    I use Chrome & just search through the address bar.

    Good luck!

  3. #3
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    Re: Automatic 4WD does not 'turn on'???

    The automatic 4wd vans have a 4wd control computer. Its job is to monitor the switch and a speed sensor. When the switch is turned on, the computer activates a VSV (Vacuum Switching Valve) and this allows vacuum to pass from a vacuum reservoir to the vacuum actuator on the transfer case. When the switch is turned on a "4wd indicator light" illuminates in your instrument cluster. When the switch is turned off, another VSV is activated and that shifts the transfer case out of 4wd. The 4wd light in the cluster will remain illuminated until you back up about 20 feet or so (this allows the auto hubs to disengage). When the light goes out, the auto hubs are released, and you know you're back in 2wd.

    If you're not getting any illumination of your 4wd light, the 1st thing to do is check the fuses. The 4wd control computer is powered by the gauge fuse (fuse #8 top row center of your fuse box) & the ECU-IG fuse (fuse #9 right below fuse #8). Reference below:



    If the fuses are good, then go to the service manual pages TF-55 through TF-61 for troubleshooting information. If you don't have a service manual, here's a link to a link to a downloadable one for 1987 vans: https://drive.google.com/file/d/1q4u...7wOD7nKyF/view. I recommend anybody with a van download this ASAP as it could disappear at any time. Enjoy. Tim

    PS: The circuit is also outlined in the electrical schematic section of the manual (reference PDF pages 1,026 & 1,027).

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    Re: Automatic 4WD does not 'turn on'???

    Thank you both so much for the quick and informative replies!

    A few things I should mention:

    The 4WD indicator light DOES turn on. However, the front wheels do not seem to be 'activated'. On the slick hill they were neither spinning out nor rolling forward. Just sitting there looking dumb while my rear tires spun out. Witnessing this while the little 4WD indicator was happily glowing on the dash got me to saying some bad words. I am sorry for saying mean things to my van. CONTINUING: If I press the 4WD button and then drive 10+ feet in reverse, the indicator light turns off. This seems to rule out the fuse issue that Tim mentioned. I am not sure what else this does/doesn't rule out however.

    At this point I'm not sure what the next step should be in my troubleshooting procedure. I alluded to the hubs earlier. I am not sure if they are locking. At the same time I figure it's possible that the problem is something else, such as the vacuum. I'd hate to fix one thing and have the problem be another. What steps might I take to determine where the weak link(s) is/are? Are there any visual/audible cues I should be looking for?

    I downloaded the service manual and am going to be cozying up with some tea next to the fire for the next few nights. That being said, I am a serious noob to wrenchin' on my own car. I have tools, patience, and a methodical style though.

    thanks again!

  5. #5
    Administrator timsrv's Avatar
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    Re: Automatic 4WD does not 'turn on'???

    Quote Originally Posted by chazlamborghini View Post
    I alluded to the hubs earlier. I am not sure if they are locking. At the same time I figure it's possible that the problem is something else, such as the vacuum. I'd hate to fix one thing and have the problem be another................

    & thus the reason everybody hates auto locking hubs. It's considered an upgrade to switch to manual hubs, so if you plan on keeping the van this is a worth while investment. This will also give you a chance to repack your front wheel bearings and inspect the brakes and other vital components (don't forget it's a 26 year old vehicle and these things should be checked anyhow). These hubs are the same ones Toyota used on the same era IFS trucks and 4 runners (26 splines), so they are plentiful. Most auto parts stores sell aftermarket brands, but I prefer the stock Aisin hubs. Here's a few links to some used ones on eBay:

    http://www.ebay.com/itm/86-87-88-89-...091f5e&vxp=mtr

    http://www.ebay.com/itm/86-95-Toyota...f7ef6d&vxp=mtr

    http://www.ebay.com/itm/Toyota-Aisin...d74ed6&vxp=mtr

    http://www.ebay.com/itm/Toyota-Aisin...384b59&vxp=mtr

    If you go this route you will also need bearing washers & nuts as the auto hub style are not compatible with the free-wheeling locking hubs. Here's a link to these (you'll need to order 2 of these):

    http://www.trail-gear.com/product/49...earing-nut-kit

    You will also need a 54mm socket to install these.

    Okay, back to the issue at hand and your questions. The way you described the 4wd cluster light going on & off suggests the transfer case is actuating/shifting into & out of 4wd. If the front wheels don't engage, the next thing to do is a visual inspection to verify the front drive-shaft, differential, and axles are there. I would also (carefully) look under the van while somebody pushes the 4wd button. Listen for the actuator on the transfer case and verify it's shifting. One way to test 4wd is to turn a tight corner with it engaged. If it's working you will get a jerky sensation (especially on pavement). On gravel you will also get some slippage of the front tires that results in some minor disturbance of the loose surface material.

    Another more aggressive approach to testing is to remove the rear drive-shaft. Doing this removes all doubt as to whether or not the front drive train is working. Tim

  6. #6
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    Re: Automatic 4WD does not 'turn on'???

    This isn't a repair reply, rather relaying an extra benefit to our vans.

    The nice thing about our vans is the fact that you don't have to get out of the van to lock in the hubs. I remember being at the bottom of Little Cottonwood Canyon, in Salt Lake City, ready to head up the hill to Snowbird. We were sitting at the stoplight and saw the "chain-control/4WD" sign. All me and my buddy had to do was open the doors and reach down and lock the hubs.
    We got some amusing looks from a couple folks watching. Also, it's been handy in the muddy desert, down in AZ in the winter, again, reach down and lock 'em in without getting out and getting all muddy.

  7. #7
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    Auto 4wd 'push button' question....

    Hello all,

    Have put about 1200 miles since acquisition on my '88 4x4 Auto LE. Neat rig.

    When acquired, push button 4wd seemed to work fine, button and dash lites come on and noticed traction and steering feel (not my first 4wd).

    Recently, I noticed when button is pushed, button lite works/comes on, but dash lite has not been regularly coming on (on demand) and I haven't felt the 4wd work with dash lite off/not on. I changed the transfer fluid today and went for a 4wd 'test' in a slick field (front tire mud burn out with looking out door to verify front wheel spin). Stopped and pressed 4wd button.

    The dash lite did not come on but button lite did and hubs didn't engage = No front wheel spin!
    Almost got stuck out there in 2wd when I really needed the 4wd. Not good, I need reliable 4wd.

    What's happening? I read the owners's and factory manual and they say nothing about the scenario in troubleshooting sections.

    I'd like to resolve this asap, got off highway excursions planned..

    Any insight appreciated and thx!

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    Re: Another auto 4wd 'push button' question....

    Is it possible that i overfilled the oil level?
    I cleaned electrical connection to transfer case (to left and lower the fill port) and noticed that oil poured out when i removed the bung (sensor?) to inspect.
    The electrical connection/bung it is lower than the fill port so I assume this pc gets oil/ lubed?

  9. #9
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    Re: Another auto 4wd 'push button' question....

    Check the vacuum lines

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    Re: Another auto 4wd 'push button' question....

    Quote Originally Posted by Chi-Town View Post
    Check the vacuum lines
    Will do and thx!
    This auto 4wd set up is new to me ( had manual lever 4wd prior).

    Any linesn particular to start looking at?

  11. #11
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    Re: Another auto 4wd 'push button' question....

    Follow the line from the actuator on the transfer case to the solenoid and to the motor.

  12. #12
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    4WD operation on 91' Town Ace Camper

    (Preface)- I went through and read through all of the threads in 4WD forum before posting, didn't find an answer as my van doesn't seem seem to come up as much and not sure if is the exact same as the other vans. Please forgive newbie/simple question.

    I recently bought a 91' Town Ace Camper, manual, diesel, RHD, 4wd w/ manual locking hubs. I didn't have the chance to see/test the vehicle before buying it. Not sure if the 4WD is working.

    I lock hubs, press 4wd button. (No indicator light comes on) I tried driving in a tight circle on pavement to see if was harder in 4wd and there seems to be no difference.

    There is a transfer case lever, assuming is for 2wd/4hi/4lo? I cannot get it to move, is in position closest to floor. (forward)

    Is there an order of operations that I'm not doing correctly? (Do I need to switch transfer case 1st, then hubs, then button, etc?)

    I don't have the ability to jack up the entire van to see if front wheels turn, I can try taking up a steeper hill or take to my mechanic, but wanted to 1st see if I'm simply not doing something right from the start.

    Thanks for
    Last edited by jhjeff; 06-30-2017 at 12:00 PM.

  13. #13
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    Re: 4WD operation on 91' Town Ace Camper

    Found a post by Tim that had fuse diagram relating to 4wd operation. Checked and was one missing, popped it in and now light comes on, transfer case enagages and 4hi/low seems to work. Off to test it on the road.

  14. #14
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    4WD button does nothing

    Hi everyone,

    Recently, I started to have some trouble to engage the 4WD on my van. When I push the 4WD button on the dashboard, nothing happens. Sometime it works, but most of the time it does not.

    I'm thinking about an electrical problem.

    I also have another potential electrical problem (but not related, I think): my tachometer goes back to zero after few minutes of driving. Then, if I turn the headlight on, or the indicators, or the wipers, the tachometer moves! (But does not indicate the correct speed.)

    I think some wires are touching each other down there, but I don't know where to start.Maybe some of you will have an idea?

    Thanks,
    Alex

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    Re: 4WD button does nothing

    Check all connections, especially the grounds.

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    Re: 4WD button does nothing

    Thanks for your answer Ace MM. For those who might have similar problems, the 4WD problem came from a blocked vacuum hose. But the tachometer is not fixed yet. The dashboard has been tested, it is apparently OK.

    Cheers
    Alex

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