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transaxle reliability in prius gen 3 info

Discussion in 'Gen 3 Prius Technical Discussion' started by Former Member 68813, Dec 28, 2012.

  1. Former Member 68813

    Former Member 68813 Senior Member

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    According to this article: Green Car Congress: Prius c hybrid goes on sale in US with entry MSRP of $18,950; new transaxle, motor technology

    Sounds like Prius gen 3 transaxle (p410) should be more resistant to stator coil shorts compared to gen 2, but less so compared to Prius C transaxle (p510).

    Here is the relevant text:
    [​IMG]
     
    telmo744 likes this.
  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    The major transaxle stator improvements came with the NHW20 over the NHW11. Only the NHW11 has shown a measurable rate of MG2 stator burn-out.

    I welcome the improvements of the ZVW30 and 'Prius c':
    • ZVW30 - mechanical and electrical characteristics similar to Camry and Highlander
    • Prius c - use of ATF cooling as well as improved stator technology and elimination of another step-down gear
    If these changes show up in the next generation Prius, buyers will have a great buy.

    Bob Wilson
     
  3. Former Member 68813

    Former Member 68813 Senior Member

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    It was my impression that transaxles do fail in high milage gen 2.

    I just wrote this in another thread:
    Luscious Garage | Blog | Gen 2 Prius (2004-2009) Transmission Failure, P0AA6, P0A92, P0A7A
    writes this:
    we can describe Gen 2 Prius transmission failure as routine, somewhere between 150-250k miles. The most common indication is trouble code P0AA6​

    While there are other potential causes of P0AA6, the most common by far is winding deterioration in the traction motor​
     
  4. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Source: Luscious Garage | Blog | Gen 2 Prius (2004-2009) Transmission Failure, P0AA6, P0A92, P0A7A

    NHW20 transaxles do fail but there appears to have been a qualitative step improvement over the earlier NHW11. Key technical changes include use of a bearing replacing a bushing, higher voltages, and a lower viscosity oil. From memory, the Toyota SAE paper claimed a 30% improvement in transaxle efficiency which lowered the heat load.

    Like many things technical, especially one as radically new as the original, NHW10 transaxle, there has been a steep learning curve and we're still seeing improvements. The original NHW10 transaxle had seals that kept the stators separated from the transmission oil. I suspect there will be more. Low hanging fruit:
    • 'dry' instead of 'wet' differential - today it sits in a pool of oil like 99.9% of all differential gears but there is no technical reason why manufacturing precision and pressurized oil couldn't handle the load and substantially reduce stirring losses.
    • filter - the initial manufacturing debris from our 5,000 mile test and carry forward suggests the oil could be kept cleaner.
    • electrically driven oil pump - provides oil at a constant pressure regardless of engine or vehicle speed.
    • lower viscosity oil - a transmission that runs cooler does not need a heavier oil that thins with higher operating temperatures.
    Improving the transaxle pays big dividends because it handles the engine power. For an engine running at say 33% thermodynamic efficiency, every 1% percent transaxle improvement has about a 3% (1%/33%) improvement in vehicle fuel efficiency.

    The Prius c transaxle has made significant improvements in rolling drag and this can be found in the EPA, roll-down coefficients.

    Bob Wilson