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Thread: Alltrac - driveshaft failure at the u joint - running in FWD

  1. #1
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    Post Alltrac - driveshaft failure at the u joint - running in FWD

    The story..
    Driving uphill a long way from home I hear a PING and some destruction coming from underneath the van. Pulled over knowing this was not going to be good. On the side of the road I looked under the van to find the drive shaft hanging (broken at the front most u-joint). Damn... I thought to myself.. This is the shaft that connects the drivetrain to the rear wheels. I wonder if the front wheels still spin. Got inside and the van still moved! I turned off the van, removed the now hanging shaft, and thought I was good to go! Tried to start... nothing.. Turns out after the shaft broke it spun freely and destroyed the starter . Got her towed to a local shop and they (thank goodness) had the starter in stock . I could not believe it!


    This was about 1 month ago.

    I have been driving the van ever since without the front drive shaft. I am talking about the front drive shaft for the Alltrac previa. Not the SADS (accessory) shaft.
    If Im not mistaken there are 2 drive shafts that enable Alltrac, front and rear. But Im not too familiar with the details.

    I have about 1000 miles on the van after this incident.

    Here are my observations for running an Alltrac in FWD:

    Highway driving: Seams to be completely unaffected, she runs great actually.

    City driving:
    This is where I have some questions of what the heck to do.
    Accelerating is not the same (expected I suppose). There is a winning noise when under normal acceleration (I assume Alltrac is trying to engage). I imagine that bracket ( that would be attached to the shaft is now spinning freely. Perhaps sending power to the rear?
    As a result, accelerating is SLOW, maybe dangerously so.
    As Im accelerating from a stop I try to be verrrrrry gentle as to not engage the spinning sound (alltrac?). I don't want to F'up the van any further...
    On one occasion I experienced this behavior that I read about on this thread.

    That shaft will whir like an A-10 until the coupling in the t-case decides to lock up. It does it sitting still in drive and unless I really give her a lot of throttle the vehicle accelerates like there's no fluid in the torque converter. Once it locks up, the whirring sound goes away and she's off like a rocket.
    This is where I get lost. I am curious about if this behavior is sustainable? On the thread listed above, they talk about locking the transfer case. I am wondering if this will be a solution for running the van in RWD. What is the solution here?

    What to do... what to do...

    Questions / feedback is very appreciated!

  2. #2
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    Re: Alltrac - driveshaft failure at the u joint - running in FWD

    cgregs and I have corresponded a little over this. I wanted to summarize here.

    His van is running RWD (front shaft is removed)
    I recommended locking the transfer as a method of protecting it while he figured out a solution to the broken front u joint.

    There was a problem with this advice...

    My 1991 transfer looks like this, with the shift shaft cap nut (upper right, 1st pic) and locking pin socket nut present...

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    cgregs 1995 Previa looks like this...
    The transfer seems to have been redesigned and the shift shaft external stuff is not there.


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    The Toyota parts diagrams suggest that the entire shift shaft was designed out of the Previa transfer case starting in 1995. 1994 seems to be the last year with the shaft.
    Can anyone else with a later model van corroborate this?

  3. #3
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    Re: Alltrac - driveshaft failure at the u joint - running in FWD

    Thanks Jonny for all your help.

    I am still trying to source this shaft for my van.

    1. Is it possible my transfer case an be locked electronically?? Thought pulling a fuse or something. Maybe Jumping something in the diagnostics box.

    2. I am trying to source a front propeller shaft for my 95 Altrac. No luck looking at local Pick-n-pulls. I am located in SLC, UT. If anyone has any leads, it would be greatly appreciated!

  4. #4
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    Re: Alltrac - driveshaft failure at the u joint - running in FWD

    Ha, I'm in SLC too. Update your profile. You can buy mine for scrap yard price to get you on the road again with AWD for the rest of the Winter (not much of one yet, eh?). I doubt I'll ever turn mine back into AWD and if I do I have other vehicles to use while I find another shaft.

  5. #5
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    Re: Alltrac - driveshaft failure at the u joint - running in FWD

    How did my old drive shaft work out for you?

  6. #6
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    Re: Alltrac - driveshaft failure at the u joint - running in FWD

    For the record, there's a viscous coupling in the center diff... the driving attributes you described align with having it. Basically, the more one side spins, the more it tightens up, up to a point. Driving around without one axle connected WILL overheat it and lead to premature failure. (No I don't know how long it'll last) As it degrades, it may act more like an open diff or it may lock up.

  7. #7
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    Re: Alltrac - driveshaft failure at the u joint - running in FWD

    Unfortunately cgregs32 has not completed his thread, so I'll do it for him. I happen to know that the replacement front shaft he bought from me and installed about a month ago was working fine right after install and had cured all the strange noises he was getting while driving without the front shaft. Personally, I think he can count himself fortunate that no lasting damage appears to have occurred from driving without a front shaft on one of the later model, non-manually-lockable, transfers.
    Several people do seem to have got away with removing a shaft (front or rear) and continuing to drive for a while, so maybe these transfers are so rugged that it doesn't matter, or the viscous coupling fails in a manner that the vehicle still drives fine in make-shift 2WD without one of the shafts and without locking the transfer. Or maybe not. I sure would like to hear from anyone who has suffered serious repercussions from doing this, but although it seems inconceivable that it is not bad for the vehicle, so far I have not read about anyone confirming it in practice.

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