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four wheel drive test

Discussion in '40- & 55-Series Tech' started by Travis_Kinney, Dec 18, 2003.

  1. Travis_Kinney

    Travis_Kinney

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    I have a 1969FJ40 and I don't think my front end is getting any power. My guess is that it is a vaccum hose. Is there an easy test to see if the fron is getting power other than putting the whole vehicle up onto jack stands? I had someone watch my wheels while I was spinning on some snow, but we couldn't tell. Here's a question though: If I am in four-wheel drive, can just one of the rear wheels be spinning out? I thought for one of the rear wheels to be spinning out one of the front ones would also if you were in four wheel drive? Any care to explain some of this?
     
  2. Bryan-71

    Bryan-71

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    Find the deeptest baddest mudhole in your area, go about half way through it and stop...it wont take long to see if your front end is engaged (ask me how I know this). Seriously, unhook your rear drive shaft, its only 4 bolts, very easy to do.
     
  3. Paul_A

    Paul_A

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    Simple with lock out front hubs: with the engine running and without locking your front hubs hit the front drive switch and go underneath and see if the front shaft is locked up. If it is--good, you got the power. If it isn't--then no power is going to the front.

    Without lock out hubs do the same thing but lift one front wheel of the ground so the wheel will turn. Again, if the front shaft rotates you have no power to the front.

    I can't tell you how many times people try this with the engine not running--there ain't no vacuum tank in these things! :doh:
     
  4. Jman

    Jman

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    Workable variation of Bryan-71's plan:

    1. Wash truck.

    2. Drive truck onto neighbor's wet lawn

    3. Engage 4wd and FLOOR IT!!!!

    4. Look at quarter panels.

    If the mud splatter is as high behind front wheels as it is behind rear wheels, front is engaging.

    Or, put it in reverse and floor it and see how far your front wheels throw out the mud.
     
  5. Travis_Kinney

    Travis_Kinney

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    Thanks. I figured there was some way to tell. Didn't even cross my mind to check the shaft rotating or not. huh!
     
  6. rgentry

    rgentry

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    You can run a temporary vacuum line directly to the transfer case
    to see if you can get it to go into 4wd. There are two vacuum
    ports on the diaphragm, I'm not sure which one puts it into 4wd
    but I can check if you want me to.
     
  7. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    Something else to consider is that the vacuum control mechanism sometimes gets corrosion on the inside, and rusts into position. There have been more than a few that I have needed to take apart to clean the levers and pivots inside of this unit.

    Verify that you are getting a good vaccum to the control bellows, before removing, and messing with it tho...

    Good luck!

    -Steve
     
  8. cruiser_guy

    cruiser_guy

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    Travis,
    Your initial assumption is correct. There is positraction between front and back axles (not side to side like a locker though). What I'd do is engage front drive, set the e-brake leave the hubs unlocked and crawl under and see if the front drive shaft will turn (you may need to give it a good twist).
    If it turns then you're not engaging if it does not turn then it is engaging! Easy!!
     
  9. lowtideride

    lowtideride

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    yeah thats the first thing i did after i got my 60...pulled into a snow covered parking lot hung my head out the window and floored it as i spun out dounuts :)
     
  10. CruisinGA

    CruisinGA

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    Uh that wasn't snow, Al. It was sand. :D
     
  11. IDave

    IDave

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    kinda rough on the P-tex bottoms of your skis....
     
  12. Jman

    Jman

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    [quote author=cruiser_guy link=board=1;threadid=8922;start=msg77630#msg77630 date=1071808302]
    Travis,
    Your initial assumption is correct. There is positraction between front and back axles (not side to side like a locker though). What I'd do is engage front drive, set the e-brake leave the hubs unlocked and crawl under and see if the front drive shaft will turn (you may need to give it a good twist).
    If it turns then you're not engaging if it does not turn then it is engaging! Easy!!
    [/quote]

    When you do this, don't put the truck in gear, just leave it in neutral!!! (I know, stupid reminder, but I had this awful vision in my head of what could go wrong. :whoops: )
     
  13. shameless

    shameless

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    I had this question/problem - suspected little to no power to the front wheels, and confirmed it after a snowstorm. It turned out my front locking/freewheeling hubs were stripped (Superwinch). I swapped them out for Warn and now have 4WD again!

    :)
     
  14. Travis_Kinney

    Travis_Kinney

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    I tried testing my front end engaging like you said and the test is simple and answered my question. First my indicator light on my transfer case wasn't hooked up so I wasn't going to go by the light coming on as an indicator. So I put the rig in neutral (with wheels chocked), unlocked hubs and reached under and could easily spin the front drive shaft. Then I pulled out the vacuum knob that engages the front diveshaft. Went out and the shaft still spun just as easy. Sure indicator that it didn't shift. After reconnecting the indicator wiring, I retightened the various vacuum lines and even tested my vacuum level (20ish). After retighten things the indicator light came on. I reached under and could turn the shaft a tiny bit, so it was diefinately engaged. Locked hubs and drove it out into the field (snow coevered of course). tried engaging the 4-wheel drive again and would work! I popped the hood and retightened all the lines and hose clamps. I feared i was on teh verge of stripping some of them if I kept tighten them. Still would transfer. I unhooked the short section of hose underneath (while lying in the snow) and retightened those clamps. Nothing. Unlocked hubs and ran through test again. Front shaft spun round and round. I finally decided to test vacuum again. I removed one of the liones off the shifter and put my vacuum guage on the line and vacuum shot up to 20ish and transfered the power to the front. So I guess my testing the first time with tehguage built the vacuum up enough to shift the transfer. That told me that my vacuum shifter wasn't working. By now my feet were frozen, but at least I was in four wheel drive and could get out of the stupid field and back into the drive way. As a celebration of figuring it out, I drove back and forth over the snow bank by the road. I pulled out the vacuum switch and have it dismantled. I plan to por15 the steel mount and replace the gaskets and should work fine. A guy yesterday told me they would check for vacuum leaks by spraying carb cleaner around the vacuum switches. If the rpm's increased then you had a leak, becuase you were essentailly sucking the carb cleaner into the engine which in turn increases the rpm. I thought that was a neat test that would come in handy. Hope this long post helps someone.