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free wheel?

Discussion in '80-Series Tech' started by sodajerk, Jul 6, 2005.

  1. sodajerk

    sodajerk

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    free wheeling?

    I have a 1997 lx 450 with lockers. My question is if nothing is lock should I be able to lift any one tire and spin it by hand or with the engine?

    Thanks,
    Russell
     
    Last edited: Jul 6, 2005
  2. Biff

    Biff

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    Damit!!! I thought this was about a free wheel. :mad: oh well I never get anything for free.

    what was the question again?
     
  3. CruisinGA

    CruisinGA

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    There is a viscous coupling, so the answer to both is yes but no.

    #1- It will be hard to spin, but it "should."

    #2- The truck will try to move, and will have enough power to push over a jackstand, so be careful. The free wheel will spin faster than the rest. I've done this before with one wheel chocked to line up control arm bolts.

    just drop the tcase in neutral to spin the tire by hand.
     
  4. Fochdog

    Fochdog

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    Your axles are open diffs (when not locked) and your t-case has a full-time planetary diff with a viscous coupling (VC) across it. The VC is a speed sensitive device that attempts to maintain the front and rear propshafts rotating at the same speed.

    Now if you lift a single wheel and try to spin it the open diff in the axle will give some (but very little) resistance. However, since the t-case is full-time by spinning any single wheel you will also be spinning the respective propshaft. This will then start to differentiate the VC and shear the silicon fluid in the VC. Depending how the VC is tuned (loose or stiff) this could require very little or a lot of force.

    I have not tried this yet in my truck ... but I will try my next chance.

    So to spin a single lifted wheel by hand ... probably not, with the engine ... probably yes.
     
  5. RavenTai

    RavenTai

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    Never put the truck in gear when on jack/stands, the truck will try to come off of them unless you have all 4 tires off the ground or have removed driveshaft to any tires on the ground

    Not exactly, even when the lockers are disengaged all 4 tires are solidly connected via 3 geared differentials, a differential has one input and two outputs, the two outputs can have very different RPMs even turn opposite of each other but the average of the outputs must match the input.

    For example if you were to lift one tire it will not spin because the other tire on that axle is on the ground, input is 0 revolutions, side on the ground is 0 revolutions so the tire in the air is limited to 0 revolutions.

    But if you were to lift both tires on one axle off the ground and spun the left tire the right tire would spin in the opposite direction, the counter rotation makes their average 0 rpm and matches the input.

    Something to note here is that as soon as any one tire, (front or rear,) comes off the ground the parking gear in the transmission will no longer hold the vehicle stopped, because of this you should always lock the CDL and block the tires of the axle that remains on the ground when jacking the vehicle. If it is the rear axle that will remain on the ground then also set the parking brake.

    Tested this out wile I had my front drive shaft out, wile on downhill portion of my driveway I unlocked the CDL and the truck smoothly rolled down the driveway wile in park.

    The Viscous coupler dampened the motion and kept the speed down, as the front and rear outputs of the transfer case were spinning in opposite directions.

    Same if the T-case in neutral the parking pawl in the transmission cannot stop the vehicle as it is disconnected from the ground.
     
  6. elmariachi

    elmariachi

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    If I jack up the driver's front on mine with my roller floorjack I can rotate the lifted wheel backward and the truck will roll backwards. If I pull it into gear it will spin the wheel as the truck moves forward. I agree...not a jackstand type stunt.
     
  7. Land Speeder

    Land Speeder InstaH8R

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    This is very good advise, and was the reason I was very surprised to see the Aussie Locker instructions read to put the truck in gear while on stands. I read it twice and then again. But it made sense to have the truck in gear when testing wether the locker was installed properly, i.e. spinning one rear wheel while holding the other to ensure proper installation. And this required the truck to be in gear. So there is a proper time and place but care must be taken. AND USE CHOCKS!
    (FWIW, I don't have a VC in my 91)
     
  8. RavenTai

    RavenTai

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    The Aussie locker instructions were probably written for the rear axle of a 2 wd or standard four wheel drive vehicle where drive to the front wheels can be disengaged.

    I cannot imagine they would ask you to do that on an all wheel drive vehicle, but as you said without the VC you are much less likely to get into trouble, I still would have put all four wheels in the air or skipped the test altogether.
     
  9. Aussie_Locker

    Aussie_Locker Supporting Vendor

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    Aussie Install


    You are correct. We do not recommend a front install in an "All Wheel Drive" or "Full Time 4WD Drive" vehicle. We state that on our web site in a number of locations. The installation instructions are for a 4WD vehicle with the ability to shift in and out of 4WD, and they apply to both front and rear installations.