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2006 Prius feels like the transmission is slipping at freeway speeds

Discussion in 'Gen 2 Prius Main Forum' started by Mike prius lover, Mar 13, 2024.

  1. Mike prius lover

    Mike prius lover Junior Member

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    Hello fellow Priusuiers, I have put over 500K miles on 3 different gen 2 priuses and have fixed all sorts of problems on them but this one currently has me a little stumped. At higher speeds, over 65 when I try to accelerate slightly the gas motor revs excessively but the car does not accelerate. It feels just like an A/T that is slipping. If I give it more throttle the gas engine bounces of the rev limiter but the car does not accelerate. It will actually decelerate up slight hills even at full throttle. The car will surge back and forth a little bit under this condition. I also get a slight burnt electrical smell at higher speeds which has been happening since I got the car at 180k miles but I could never pinpoint the cause. If I keep it at higher throttle levels it will quickly deplete the hybrid battery down to 1 bar but the battery seems fine otherwise. If I back of the throttle when It feels like it starts slipping then it works fine but it wont go over 70mph unless I'm going down hill. I have checked all the hybrid cell voltages and they are all right around 8v. I have no warning lights currently on. The car has 280k on it and the gas motor is tuned up and runs great. Trans fluid was full in both transmissions. Coolant levels are full and I confirmed that the inverter coolant pump is working. So I figured that MG1 or 2 was going bad in the transmission so I got another trans from a wrecked car and replaced it. It still does the exact same thing with the newer transmission. Any ideas?
     
    #1 Mike prius lover, Mar 13, 2024
  2. Brian1954

    Brian1954 Active Member

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    Check for exhaust restriction.
     
    #2 Brian1954, Mar 13, 2024
  3. Tombukt2

    Tombukt2 Senior Member

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    When I had the revving like I was wearing out a clutch step on the gas car would rev up not really go anywhere My '09 was doing this and doing this exact thing while the hybrid battery was failing miserably was actually doing this before the fan came on full time and the battery fell on its face when it was removed it was disgraceful looked horrible but anyway that's exactly what would happen we'd try to speed up with the car and the engine would rev into Oblivion and the car would go nowhere actually it was better if you took your foot off the gas and then slowly brought it back up but it was really hard to navigate while it was like that The minute I dropped the new battery in at the Toyota dealer parking lot that ended immediately quite noticeable drove out the parking lot and gave it to gas and the tire squalled We were quite shocked.
     
    #3 Tombukt2, Mar 13, 2024
  4. Mike prius lover

    Mike prius lover Junior Member

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    Ok, were you getting any warning lights on the dash before you put the new hybrid battery in the car?
     
    #4 Mike prius lover, Mar 14, 2024
  5. Tombukt2

    Tombukt2 Senior Member

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    Well yes I was having the whatever the bad battery code is I mean I had multiple modules that were way out of whack It was the original battery 2009 car I guess the almost the midpoint of the pandemic all this was happening and I believe that was about it now during this time I was also having trouble with the break actuator so that puts on all the yellow lights predominantly I also had a check engine for the PO420 which the car has had most of its life The fan was running all the time in the back anytime the car was running etc all the signs were there and we were down with getting a new battery versus used and all the business because this is a work vehicle now that I have three or four of them I have rebuilt batteries in two that are running strong and going like gangbusters how long they'll last I don't know.
     
    #5 Tombukt2, Mar 14, 2024
  6. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    You might check the battery ECU. (it has its own brain down there)

    There have been problems with failing connectors on that module, and it can fail in different ways. In blunt terms, it may not be working well enough to notice a battery problem, and your other symptoms line up well with 'spent hybrid battery.'

    Even just looking at the age of the car- not many hybrid batteries still function well at that age.
     
    #6 Leadfoot J. McCoalroller, Mar 14, 2024
  7. Mike prius lover

    Mike prius lover Junior Member

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    Well thank you all for your reply's. I spent this morning troubleshooting a little more and it does seem to be the Hybrid battery. When I drive up a long steady hill on my road the battery goes from about 3/4 full charge down to 1 bar in about 10 seconds and then it really starts over revving. When I checked the exhaust for restrictions I found that the muffler had a 3 inch diameter hole in the top of it that was heating up the whole trunk floor to over 200 degrees which I'm sure wasn't good for the hybrid battery. Funny thing is when I took off the whole rear muffler assembly, the car was not any louder at all. Also the replacement transmission that I put in is leaking coolant from the main shaft seal, so I would have to take the transmission back out to fix that. On top of that the A/C has been out for years due to a leak in the evaporator so it might just be time for the junk yard
     
    #7 Mike prius lover, Mar 14, 2024
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