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Toyota Sienna AWD Problems/Questions



  • wwestwwest Posts: 10,706
    Apples and Oranges....

    Our 2000 AWD T&C has a VC, viscous coupling, to the rear driveline that is ALWAYS in effect at a reasonably high level, additionally the fluid is obviously formulated to have a very high "attack" rate, rapidly increasing torque coupling coefficient, upon front wheelspin.

    Whereas the Sienna has a simple open center diff'l and relies on TC braking (and engine dethrottling) to apportion engine torque to the rear driveline ONLY AFTER front wheelspin/slip occurs.
  • ateixeiraateixeira Posts: 72,587
    Actually, this article implies the Sienna still uses a full-time system just like Dodge's. I'm not sure there is any difference.
  • Our 2005 SLE AWD has 45,000 problem-free miles if you discount the run-flats that Toyota replaced at 24,000 miles under the revised bumper-to-bumper warranty. We live on top of a ridge in mountainous WNC, and AWD is more of a precaution than a regularly-needed feature, because our snow is rarely more than 6 inches at a time and it melts quickly...but it is a real issue when your are climbing a winding, 14 % grade to get home.
    I have never spun a tire in the snow or slush or off road when camping. The ride is a little too low to attempt serious off-roading in a Sienna, but its the most reliable people and luggage hauler on the market that isn't a giant SUV. We have made trips to SC beaches, the Gulf Coast of Florida , Louisiana and Michigan, and the same car that enables our family to quietly and comfortably eat up interstate at at 75 mph (while my wife reads or works on the laptop via wireless data modem,my mother-in-law reads or sleeps, the 17 yo and the 11 yo watch DVD's or listen to whatever they want on headphones) also allows us to ride along with a great sense of safety and security in snow and heavy rains. The seats are so comfortable and supportive that I choose to drive the Sienna on my business trips to Eastern NC, etc.
    My average over 45,000 is 18.9MPG, and we get around 22 MPG on long trips with 5 people and all the luggage, etc. That is the same as my other vehicle , a 2004 Subaru Forester XT, which requires premium fuel. The Subaru is a lot more fun to speed up, down and around mountain roads, but it was a crowded, packed situation going to the beach.
  • wwestwwest Posts: 10,706
    If you don't already have the practice of shifting your F/AWD Sienna into neutral as you approach a curve on your downhill drive when the roadbed is slippery you might want to consider adopting same.

    Or just keep this thought in mind when the day arrives that your F/AWD Sienna begins to PLOW toward the outside, DROP-OFF side, of that curve.
  • ateixeiraateixeira Posts: 72,587
    I don't see how that would help, to be honest.

    Keeping it in gear and using engine braking will shift the weight forward, reducing understeer. Tapping the brakes may help, too.

    If you put it in neutral and coast you will have to use the brakes alone.
  • wwestwwest Posts: 10,706
    "Keeping it in gear and using engine braking will shift the weight forward, reducing understeer."

    Yes, that is true, VERY true, right up to the point wherein the level of roadbed traction is no longer sufficient to support both the braking and lateral (stearing/directional) loading.

    Believe me, it WILL happen. You can either be prepared for the event, ready to quickly shift the transaxle into neutral (as recommended by the AAA), or have previously shifted onto neutral. A second bit of advice is that if you do not have VSC and your FWD or F/AWD vehicle begins to understear then you can apply the e-brake, parking brake, lightly to slow the vehicle just enough, hopefully, to bring the vehicle back into control.

    With VSC the rear brake(s) will be applied automatically in this instance.

    "If you put it in neutral and coast you will have to use the brakes alone."

    Yes, but you can alleviate the effects of actual braking virtually INSTANTLY. Alleviating the adverse effects of braking on the front tires by shifting the transaxle into neutral and then waiting for the transaxle to actually complete the shift is not so quick.
  • ateixeiraateixeira Posts: 72,587
    Fortunately VSC is now standard. Overdue if you ask me!
  • I drove a Ford Explorer right off the side of the mountain in low 4WD 1st gear, at 5 mph, at the hairpin directly below our house. My neighbor did the same in her AWD Outback. In addition to verifying our life insurance and building a retaining fence with locust logs, metal posts and anchored cable, we did a survey and I believe WWEst is exactly corect. When you are in a steep descent and have ABS and VSC, the best thing you can do when descending a steep grade on a low traction surface, in addition to not letting your speed get too high to start with, is put the tranny in neutral and let the computer adjust your brake effort.
    Juice, great to see another guy with a Sienna/Subaru family!
  • ateixeiraateixeira Posts: 72,587
    Yep, the van has served us well.

    We liked the Tribeca but it just isn't big enough for what we wanted. This weekend we took another family with us to our beach condo, 3 hours each way, and everyone was comfortable, with room for their luggage.

    When it snows, we have the Legacy. My wife stays home, so we really don't need 2 AWD vehicles.
  • Is the transfer case required a separate oil or is it a part of transmission?
  • ateixeiraateixeira Posts: 72,587
    I'm not sure, but I imagine the system is sealed. You'll probably have to change the gear oil in the rear differential, though.

    On my Subaru it was fairly simple, remove two bolts, drain, replace one bolt, fill, replace the 2nd bolt. The "fill" part is a little tougher than it seems because if you are under the van you have to pump oil up into it, but I got a $7 hand pump that did the job.

    Synthetic gear oil was $4 for the one quart required, so we're talking about an investment of a whopping $11. ;)

    Gear oil stinks to the high heavens, so take a shower before you come in contact with your significant other. :D
  • wwestwwest Posts: 10,706
    No "transfer" case in the traditional sense, but a PTO, Power Take Off, case. And yes, it is separately lubed, with fairly heavyweight gear oil, but I doubt if it needs to be serviced EVER. At ~65,000 miles the gear oil in my 2001 AWD RX300 PTO case (includes VC, Viscous Clutch) remained clear and non-odorous. Yes, I said CLEAR.

    Silicon gear oil..??

    And gear oil doesn't STINK unless it has been subjected to extreme HEAT, which is not the normal case.
  • ateixeiraateixeira Posts: 72,587
    Oh, man. You should have seen the stuff that I drained out of my Miata. Just 26k miles, too. To be fair, it was 8 years old. It has a viscous limited-slip rear diff, FWIW.

    It looked like melted chocolate, too, coming out.
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