1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Transmission knocking at start-up

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Cadenza, Apr 13, 2016.

  1. Cadenza

    Cadenza Member

    Joined:
    Nov 5, 2013
    109
    28
    0
    Location:
    LALA Land
    Vehicle:
    2005 Prius
    Model:
    N/A
    Hi everyone,

    Just last night my '05 Prius transmission developed an intermittent knocking/juddering sound at start-up. A few seconds after Ignition ON, the ICE would normally start and the knocking/juddering sound comes alive. In Drive mode at low speeds and gentle throttle, it feels as though the transmission cuts in and out. It seems fine at higher speeds. So far there's no warning light on the dashboard or the MFD.

    Is this the early sign of failure cited by Luscious Garage...
    Gen 2 Prius (2004-2009) Transmission Failure, P0AA6, P0A92, P0A7A - Luscious Garage | Hybrid Specialists

    Is it possible to read transmission trouble codes with the Mini VCI or must I bring the car to the dealer for a diagnostic?

    Maintenance: 2 fluid drain & refill (33k, 101k) and 1 coolant change at 68k done by Toyota dealers.
    Current odometer: 152k

    Any idea on how to diagnose this would be appreciated.
     
  2. ericbecky

    ericbecky Hybrid Battery Hero

    Joined:
    Mar 12, 2004
    4,365
    3,209
    1
    Location:
    Madison, Wisconsin
    Vehicle:
    2005 Prius
    Model:
    Two
    If you have the scanner, go ahead and do a Health Check scan, just to see if anything is in history.
    It'd be worth the effort.
     
    gasgaraget likes this.
  3. edthefox5

    edthefox5 Senior Member

    Joined:
    Jul 25, 2007
    10,096
    4,795
    0
    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two
    Luscious is referring to a stator winding short which will instantly throw a dtc as a hi volt fault. Since you do not have any dtc's to clear I doubt any are logged so it probably is not a hvf but more probably a mechanical failure in the trans.
    I would suspect low trans fluid that has caused a bearing to fail. That may be caused by a leaking seal where the cvt joints enter the differential section.
    Have you ever monitored for a leak under the car of red fluid? if you garage the car always keep a big piece of cardboard under the front of the car for just this reason.
    if it was me I would immediately pull the trans fluid and inspect for pieces of metal in the fluid and a big clump on the magnet. Easiest to put the fluid in a big wide container and put it in the sun and see if any gold is shiny in that pan. Because alot of the metal may not be ferrous and the magnet may capture it. No metal the mechanical may be ok.
    Btw, how do you drive the car? Are you hard on it with hard launches and see alot of mountains?
     
  4. Cadenza

    Cadenza Member

    Joined:
    Nov 5, 2013
    109
    28
    0
    Location:
    LALA Land
    Vehicle:
    2005 Prius
    Model:
    N/A
    Today's driving:

    1. Cold start, stop-go traffic speed up to 40 mph, 5mi... no juddering
    2. Warm start, freeway speed up to 70 mph, 6mi... no juddering
    3. Warm start, stop-go traffic speed up to 30 mph, 2mi... no juddering

    Ed -
    Thanks for the clarification about Luscious. No leak for both ICE and Transmission. I crawled underneath again today to give it a hard look and no oily/sooty spot anywhere on the tranny, including the inner CV joint area. I also checked the ATF at the filler hole and it's at the right level and the color is still bright red.

    I'm easy on the car and most of the daily driving is on flat roads. I've been high-beamed and honked at by other Prius drivers... imagine that !!!. But it's seen three road trips since last May...

    1. SoCal - Zion NP - Yellowstone and back (3000 mi, lots of steep hill climbs in Yellowstone, 40-65*F temp)
    2. SoCal - Zion NP - Bryce Canyon and back (1200 mi, moderate hill climbs, 15-65*F temp)
    3. SoCal - Yosemite NP and back (700 mi, moderate+ hill climbs, 35-65*F temp)

    Tomorrow I will drain the ATF. If the Prius fails on me, this would be the second Toyota (2 of 2) that's had tranny and/or engine gone bad around 150k... fingers crossed.
     
  5. edthefox5

    edthefox5 Senior Member

    Joined:
    Jul 25, 2007
    10,096
    4,795
    0
    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two
    Bright red fluid infers a recent change. May not be trans issue at all. May be the motor.

    Go on youtube and search Pius Inspection Mode. That's how you can get the car to run at idle. Have someone start the car while your under the hood giving it a listen. See if you can pinpoint the noise. Have them start the car while your under it in the front also so you an listen real good to the trans. Let it run in inspection mode and listen to it.
    It may be the motor that's knocking or shuddering. I would still pull the trans fluid.
     
  6. Cadenza

    Cadenza Member

    Joined:
    Nov 5, 2013
    109
    28
    0
    Location:
    LALA Land
    Vehicle:
    2005 Prius
    Model:
    N/A
    I think I may have found the culprit.

    Spark plug #4...
    [​IMG]

    I replaced the plugs 6k ago at 147k. The old #4 plug had brownish/rusty stain and oxidation from water leaking through the coil pack rubber grommet. I thought I had cleaned the plug hole well enough. Apparently the crush washer of the new plug wasn't sitting against a clean surface. Combustion gas leaked through the washer and mixed with rain water (El Nino) to form a dense sooty layer. This may have caused the ICE to misfire, which yielded intermittent slacking of the chain in the transmission. So I hope this is what caused the knocking sound.

    Also did a drain & refill of the ATF and everything looked normal. At 52k of service the fluid has a darker shade of red when compared to new. The magnetic drain plug has the usual clump of fine ferrous powder and there were some shiny particles at the bottom of the bucket... but less than what I've seen from traditional Automatic slush boxes.

    Drain plug...
    [​IMG]
     
    #6 Cadenza, Apr 15, 2016
    Last edited: Apr 15, 2016
    kenoarto likes this.
  7. Cadenza

    Cadenza Member

    Joined:
    Nov 5, 2013
    109
    28
    0
    Location:
    LALA Land
    Vehicle:
    2005 Prius
    Model:
    N/A
    My generic scanner doesn't work with the Prius. The Mini VCI is on its way. Be fun to see what it can and can't do.
     
  8. ericbecky

    ericbecky Hybrid Battery Hero

    Joined:
    Mar 12, 2004
    4,365
    3,209
    1
    Location:
    Madison, Wisconsin
    Vehicle:
    2005 Prius
    Model:
    Two
    Ewwww. Cadenza, that is one nasty looking spark plug. Good find!

    That would have been hard for us online armchair to find from here.
     
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    18,198
    6,461
    0
    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    So did you replace the #4 spark igniter as well as the plug? If the plug looked so nasty, what does the spark igniter look like? Also, you should not allow the #4 spark plug well to continue to fill with water.
     
  10. Cadenza

    Cadenza Member

    Joined:
    Nov 5, 2013
    109
    28
    0
    Location:
    LALA Land
    Vehicle:
    2005 Prius
    Model:
    N/A
    I'm reusing both at the moment. The plug's firing tip has the same shade of light brown as the others as well as the old set, so it should still work. Took a while to scrub the crud away. I switched ignition coils #3 and #4 to isolate possible misfiring and will replace the one that's faulty. If everything goes well, I would still check on it again in 2k-3k.

    Didn't take a picture of the ignition coil. It had rusty stain and moisture on the outside of the rubber sleeve that fits over the ceramic insulation of the plug. The soot hasn't yet traveled up to the upper tip. Using a torque wrench I found out the plug had backed out a bit. There was enough soot on the thread and washer to weaken the plug's contact with ground (-) which caused it to miss.

    I taped the seam of the plastic cowl (water dam) before El Nino swept through SoCal but water still got it. Thinking of designing a shield to fit over the coils somehow.
     
    #10 Cadenza, Apr 15, 2016
    Last edited: Apr 15, 2016