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    craigk Member

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    Anyone ever thought of modifying a Prius to make it part-time 4 wheel drive? Most of the time my Prius with snow tires is ok, but it would be great to have it here in Minnesota. Don't want the larger SUV hybrids, just the ability to get power to the rear wheels to get out of snow once in awhile, or not get stuck going up the incline in my own driveway. Maybe wheel hub motors? Only use at slow speeds?
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    cyclopathic Senior Member

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    it is probably too much, it would be cheaper to get a diff car.

    New 2013 Mazda CX-5 coming in spring looks good with promised 40MPG highway. EV RAV4 is coming too.

    If I were to live in show belt I'd carry snow chains, Z-chains are rated up to 45MPH(?)

    Problem with Prius there is not enough clearance with some snow you'd get stuck even with 4-wheel drive.
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    dogfriend Human - Animal Hybrid

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    walter Lee Hypermiling Padawan

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    The primary advantage of a 4 wheel drive system is having power distributed to all 4 wheels giving the drive force maximum traction-grip on the road. This means increasing the upper end of the torque on the transmission (especially at low speeds). Continuous variable transmission(CVT) designs like the one being used by Prius/ Highlander while more energy efficient have a lower upper end torque than geared transmission. A geared transmission would be the better choice for a 4 wheel drive system. If you wanted a vehicle with a 4 wheel drive system (or towing capacity) a hybrid using a geared ratio transmission (manual would be better than automatic) would be a better design choice. Toyota's Hybrid Synergy Drive (HSD) Electronic Computer Unit(ECU) would have to be reprogramming and redesign for a 4 wheel drive hybrid because it is based on the premise that a CVT system is being used.

    Hyundai's BlueDrive Hybrid System is based on geared ratio transmission but they dont have an all wheel design as of yet.

    Nissan has an all wheel drive hub motor Battery electric vehicle commuter prototype but it is still in in the car show stage - its not designed to be an all-terrain vehicle so my guess is that Nissan's ECU programming of its prototype is pretty basic and that the prototype's code is no where close to handling the complexity all terrain driving.
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    JimboPalmer Tsar of all the Rushers

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    No part of the Gen 3 or v transmission is not via gears. No cone and belt, no friction points, all gears. (Gen 1 and 2 also no not use any friction points or cone and belt but they have a chain in the final drive)
    [IMG]


    Gen 2 on left, Gen 3 on right.

    http://eahart.com/prius/psd/
    Explanation of CVT using fixed gear ratios.

    Those Toyotas (and Lexus) hybrids that have all wheel drive, just use an additional electric motor at the rear of the car.
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    xs650 Senior Member

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    I addition to what Jimbo said, there are two very different approaches to 4WD. One is the pull through anything heavy duty approach you refer to, the other is a much weaker system intended to give primarily street driven vehicles some stra driven traction on snow, ice and other slippery surfaces. They come with a warning to not do serious off roading with them. That is also done with some mechanical 4WD systems
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    LIPriusFreak Can I haz JDM?

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    I'd like to turbo my acura legend and make it RWD but it just doesn't make for financial or common sense....

    just buy a subaru and call it a day :D
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    craigk Member

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    Yes, those Subarus are great, especially the new 2012 Impreza with 27/36 mpg.

    A lot of mods to the Prius don't make financial sense but people do them anyway!
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    cyclopathic Senior Member

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    craigk Member

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    cyclopathic Senior Member

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    I've only been to MN on a couple occasions, crossing state on way west around July 4th. It was cold! hate to think how it is in winter.

    as was pointed out trading your Prius for Saburu or upcoming CX-5 could be an easy solution. Another option is to carry traction mat and portable shovel good luck
    [IMG]
    http://www.google.com/products/cata...a=X&ei=xXC-Tq6hMafx0gGi-eHxBA&ved=0CG4Q8wIwAA

    CORP-020 - German Entrenching Tool Steel Wooden Handle Blade and Pick
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    walter Lee Hypermiling Padawan

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    The design theory that I've read is to avoid belts-pulley systems because they could be prone to slippage at the high torque range and chainlink-gears systems because they could could be prone to linkage breaking due to high torque. How much torque the HSD chain could handle would be key in making the conversion. That being said - Someone probably has already figure that out since there are HSD AWD designs out there in the form of ...

    2012 Lexus RX 450h Hybrid (Part Time AWD)
    2011 Toyota Highlander Hybrid (4WDi opt)

    I'm not sure if this is OT but because the original poster posed a 4WD modification because of snow/ice - I thought I mentioned that one of the early Prius warnings/complaints that I've read before is that the Prius electric drive will automatically shut down once it senses that the the drive wheels are spinning at high speeds (no traction) when the Prius is stuck on the ice/snow and the driver panics presses the accelerator too hard. I read that the Prius shuts down the electric drive when it senses that the wheels are spinning without gripping the road to avoid burning out the electric motors.
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    JimboPalmer Tsar of all the Rushers

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    So far as I know, there is just an additional electric motor in the back, no 'drivetrain'.

    Since there is no clutch, the load once the tires finally 'grip' is very high.

    [IMG]

    With epicyclic gearing, you just increase width to allow more torque and HP.
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    Britprius Senior Member

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    The graphic shown is not the set up for the Prius, the output shaft is the ICE input, The prime mover shaft is MG1, Mg2 is on the outer ring and electrical power goes from MG1 to MG2 not the other way as shown.
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    JimboPalmer Tsar of all the Rushers

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    Correct. I was looking for a picture that allowed you to visualize additional width in epicyclic gearing, many examples do not aid thinking about width.

    Even in video designed to show off the real PSD, it is hard to visualize more width
    [ame="http://vimeo.com/24929679"]prius planetary transmission on Vimeo[/ame]
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    Britprius Senior Member

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    Thanks Jimbo I was really concerned that some one less educated about the Prius would take the graphic to be that of the Prius PSD.
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    seilerts Battery Curmudgeon

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    Suggestion: winch. It would not be too hard to fabricate a mount for the front that is attached to the reinforcement (you will have to drill through the bumper and foam absorber), and it should also be possible to do it in such a way to attach it to a 1 1/4" receiver hitch in the back if you need to be pulled backwards. You could cheat and use a portable winch that attaches to the front tow hook as well. Just make sure you have an Optima yellowtop to provide the 12V power.

    Autosocks often mean the difference between making it up the hill or not, as an alternative.
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    craigk Member

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    That Autosock is interesting, not sure if better than my Hakkapeliitta snows though?? If I need the winch it's serious trouble!:eek: I'm just looking to get out of deep snow parking spaces or up my steep driveway in extreme conditions.
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    cyclopathic Senior Member

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    if you get deep snow IMHO low clearance would be the culprit. Autosock or Z-chains are not gonna make a dent when wheels are up in the air.

    How often do you get more then 5" snow? do you have to go to work when it falls? do you have a second car in family? maybe you need a snow blower for your driveway?
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    seilerts Battery Curmudgeon

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    That's why the man needs a winch!!!

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