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Thread: Bad viscous coupler, disconnecting front shaft

  1. #1
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    Bad viscous coupler, disconnecting front shaft

    My 92 previa's viscous coupler bit the dust. I have no use foe the awd and certainly dont want to pay the big bucks to fix it. After doing a lot of online research and struggling through conflicting reports I thought I would give it a try myself. Thought someone may benefit from my experience. First I simply took off the front shaft. The van seemed to drive fine but when I would put it in park, it could still (somewhat reluctantly) roll. Not wanting to rely on my parking brake for safety reasons (no, not having the van roll over the neighbor kid, I mean not having the brake lever impale me in the butt every time I get out of the van (dumbest design on the Previa!)), I decided to try locking the fork shaft. There is another threat here with pictures of the service manual showing how to do that, but it was really easy. Remove the locking pin that can be found facing straight down through a hole on the sheet metal protective covering of the transfer case, then remove the cover for the fork shaft ( it is I think a 17mm nut/cap facing the back of the van on the back side of the transfer case, then pushing the shaft .59 inches towards the front of the van and replacing the pin and cover. I had a little trouble at first getting the locking pin back in, but then I wiggled the yoke that once had my front shaft attached and it went right in. Everything is working great now. I'll try to remember to check back in and let you know if it continues to work fine, but another fellow here got 12000 and going miles on his that he did the same on.

  2. #2
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    Re: Bad viscous coupler, disconnecting front shaft

    1,000 miles and all is fine

  3. #3
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    Previa 5 Speed M/T Alltrac, 91
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    Re: Bad viscous coupler, disconnecting front shaft

    This is definitely the way to do it - removing the front shaft AND locking the transfer - rather than merely taking a drive shaft off and hoping the transfer behaves the way you want it to.

    Locking the transfer shift fork moves the shift fork ring gear into a position where the front and rear shafts are mechanically forced to turn together AND bypasses the entire viscous coupling (or whatever it is) part of the transfer mechanism.

    For other readers, see thread https://www.toyotavantech.com/forum/...=disabling+AWD post #10

    My Previa has just under 40,000 miles in this mode - transfer locked/no front drive shaft.

    PS - piglet - thanks for updating us on your success so far. Maybe you could edit your post in the other thread where you say you can't get the pin into the shaft - let people know how you did it. Could be helpful to someone who doesn't see this thread.

    PPS - if you truly will never use AWD again there is benefit to getting the front hubs from a scrap yard 2WD previa and removing all the front axle AWD stuff ... better gas mileage and tons more room under the front of the vehicle.

    PPPS - if the hand brake lever hits you in the butt, the cable may need adjusting or the rear shoes may be getting really thin.
    Last edited by Jonny; 12-19-2018 at 03:23 PM.

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