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T-IV or WS in NHW11? analysis?

Discussion in 'Gen 2 Prius Technical Discussion' started by ChapmanF, Apr 23, 2008.

  1. ChapmanF

    ChapmanF Senior Member

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    With a recently acquired used NHW11, I'm about ready to change the tranny fluid on general principles, which leads to a couple of questions:

    The original spec fluid is T-IV. I've read some PC posts in favor of replacing with WS. Is there consensus that this is a clear win without undesired effects? Has Toyota expressed any official opinion on using WS in an NHW11? (I once lived to regret following advice in a different forum for substituting fluid in a different car....)

    I see that there's been some interest in analysis results. Bob Wilson's name (again) comes up. Is that interest still ongoing? Should I save a sample?

    The service history I got with the car appears incomplete, so although I don't see any record of a prior fluid change, I can't be sure whether this is original fluid at 125k or has been changed before and when. That might make it hard to interpret the analysis results (though perhaps an age could be estimated by comparing the results to others with known ages).

    -Chap
     
    #1 ChapmanF, Apr 23, 2008
  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    No official word although some service departments have done Type WS on their own. As long as you avoid Amsoil ATF, you'll be OK.

    The tradeoffs are this:
    • Type T-IV - wears to viscosities similar to Type WS in ~30k miles
    • Type WS - lower initial viscosity that seems to be what Type T-IV becomes
    I don't need any more Type T-IV samples but strongly recommend that you have a sample container and save one during the drain. You may find reasons on your own for analysis and having a sample makes a future analysis possible.

    The most important thing is to get a fresh gasket; drop the pan; and inspect for debris. If you see evidence of a problem, having the sample allows you to see what wear materials were in the oil. In a severe case, you may decide to run say 2-4,000 miles and do a second change. The first is treated as a flush to help get the stuff out.
    Keep a sample and check the pan and you'll be OK. If you see more stuff than you are comfortable with, run a month or so and do a second change.

    Bob Wilson
     
    #2 bwilson4web, Apr 23, 2008
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Chap,

    I agree with Bob that you definitely should drop the pan so that you can see what debris is within, and clean the pan and magnet. If you see more than very fine metallic powder, this is evidence that your transaxle is starting to disintegrate.

    Since Toyota does not recommend ATF WS for the Classic transaxle, my recommendation is to stay with ATF T-IV.
     
    #3 Patrick Wong, Apr 23, 2008
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