Replaced my tired transmission

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by zsolar, Dec 4, 2017.

  1. zsolar

    zsolar New Member

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    I got my '08 a few years ago with 100K miles. It's now at 150K miles. When I got the car, I thought it sounded just a little loud, but I had nothing to compare it to. Over those few years, I became progressively more concerned with what I thought was increasing levels of unusual noise up front. There was a whining noise under load at 50+ mph, but it was not extremely loud or alarming. Overlaid with this noise was more of a low pitched noise that I could both hear, and at times, feel as a rumble at very low speeds. Again, not especially alarming but I started to worry about the possibility of total failure and having someone in my family get stuck somewhere.

    I used an array of microphones to record the sounds at each wheel bearing and at the transaxle. It was clear that the whining, gear-like noise came from within the transaxle, but I could not pin down the source of the rumble. Thinking it was the left wheel bearing, I replaced that - no improvement.

    Eventually, I decided to swap the transmission with a used one that had 74K miles. All the noises are gone! I was hoping for that outcome, but what I did not expect was how much better the car drives. It has more power and it is getting significantly increased mileage (from ~44mpg to 49mpg now).

    I took apart the old transmission to see what was wrong. The fluid did not look especially bad (I had replaced it when I got the car). Everything was intact. Notable was roughness in one of the big bearings in the shaft that drives the differential. Additionally, the differential gears looked quite worn and the differential bearings had excessive friction. I'm not 100% certain that those observations were really indicative of the problem, but it seems likely.

    This was a fun weekend project with a great outcome. Having searched all the forums, I think this set of symptoms is not very common, but maybe others just keep going until it fails outright. I hope this is helpful for others who have these symptoms and have ruled out all the easier and cheaper possibilities (mainly wheel bearing, tire and axle issues).
     
  2. JohnStef

    JohnStef Member

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    Hello zsolar
    The trans on my '04 went away from me last night. Pulling into traffic there was a snapping sound and rattling under the car. It sounded like the car had dropped a half shaft or something. I looked and there was nothing on the ground, it was internal. The car makes no forward or reverse motion, just a light ticking/slapping sound.
    Could you outline your experience removing and swapping the transmission? I'm pretty sure I can get a used replacement locally.
     
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  3. Dxta

    Dxta Senior Member

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    There are several ways you could replace the transmission.
    1. You could remove the whole assembly, engine and transmission from the hood, then you start with the swap.

    2. You could only remove the transmission, detached from the ICE, while the engine is still in the hood.

    You just remove the engine crankshaft pulley, so that the engine can be shifted sideways to creat the needed space to remove the transmission.

    I prefer this method, just in case I'm in a far away area working on a broken down Prius.

    Remember to replace the transmission fluid, as you get a replacement one.
     
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  4. Dxta

    Dxta Senior Member

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    In this swap, did you get any codes or signs on the dash?
     
  5. edthefox5

    edthefox5 Senior Member

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    Sounds like the chain inside the trans snapped. There's many complete posts about trans replacement. Use search button up top.
    I know one thing that will help is to have a 1/2 inch impact gun preferably ac powered. Makes quick work of really tight bolts and nuts. Toyota really socks bolts on.
     
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  6. Dxta

    Dxta Senior Member

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    Correct me pls. I don't think the Prius transmission has a chain drive in it. Maybe, one of the sun/planetary gear set teeth, must have broken off?
     
  7. edthefox5

    edthefox5 Senior Member

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    Chain driven.
     
  8. Dxta

    Dxta Senior Member

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    Thanks for the corrections sir!

    Thought was gear meshed.
     
  9. zsolar

    zsolar New Member

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    Like others said, you can search and find some info in these forums. My post here has a link to what I found to be the most useful guide for this along with a few tips I added. I removed only the transmission, so I can't compare the effort of removing the entire engine/transmission, but I think there is no way that would be easier. Also, I don't see any reason to remove the crankshaft pulley as Dxta suggested- there is room to remove the transmission without doing this.
     
  10. JohnStef

    JohnStef Member

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    VERY helpful, all of the above!
     
  11. JohnStef

    JohnStef Member

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    no codes, just put an order in for the local yard to pull a 2007 trans. And thanks for the tips above.

    The car currently has no codes when powered up - seems a little strange, but I'm not complaining. That is one reason why I'm going after the repair rather than scrapping it. The engine runs well, the only systems in the car that has issues are AC and Cruise. When this is complete, those are the next 2 issues to resolve.
     
  12. edthefox5

    edthefox5 Senior Member

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    AC and cruise are basically disabled if the car has a bad hybrid battery. Give that a close look. Would suck to replace the trans only to find the hybrid battery is bad too.

    Its only the most common post we see now. It may not be "bad" but just really really tired and getting ready to be bad,.
     
  13. uart

    uart Senior Member

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    The transmission includes both the planetary "power split device" as well as the final drive (which is basically a regular differential). The outer gear (ring gear) of the PSD is connected to the final drive via a short chain drive.
     
    #13 uart, Mar 2, 2018
    Last edited: Mar 2, 2018
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  14. ChapmanF

    ChapmanF Senior Member

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    Just for extra clarity for others who might read the thread ... Gen 1 (2001-3) and Gen 2 (2004-9) include a chain in the transaxle. Gen 3 (2010-15) and Gen 4 (2016-) do not.

    The chain in Gen 1 and Gen 2 is seriously heavy ... I don't know that I would assume it necessarily broke, before any of the other breakable things in there. It may just be that something broke.

    -Chap
     
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  15. edthefox5

    edthefox5 Senior Member

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    I agree the chain probably didn't break but Luscious has discussed broken chains so it does happen. The OP's explanation of the sound sounded alot like maybe a chain broke,

    Its a moot point though as its totaled. Rare the diff wore out it may have seen heavy duty abuse. If you keep halfway decent fluid in it it may go 250,000 miles.My suspicion is it lost a inner cv joint somewhere in its life and was run low on fluid. And then sold. But I'm naturally suspicious.

    Join toyota.com/owners and post the vin and you will see every service event the car has seen in an authorized toyota dealer. May discuss issues with the trans.
     
  16. JohnStef

    JohnStef Member

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    perspective:
    2004 Gen 2, at least 3rd owner, changed trans fluid at 293000
    current miles 335000 miles (odo quit at 299999)
    2nd battery (used from 180000 2007)
    There is clatter in the tranny now as it powers on in neutral.
    I will be exploring the cause of failure when this is on the table and open. This is going to be like a kid taking apart alien tech.:D

    I see that zsolar says that the axle nut can remain attached to the hub to remove the 1/2 shaft, this is also my plan.
    Also I plan on removing the trans only and lower it down to the floor.
     
    #16 JohnStef, Mar 3, 2018
    Last edited: Mar 3, 2018
  17. ChapmanF

    ChapmanF Senior Member

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    There was some post years back, IIRC, where somebody reached in through the bell housing access hole and found pieces of the springs from the torque damper.

    -Chap
     
  18. JohnStef

    JohnStef Member

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    zsolar and others, seems like I read that removing the wiper motor assy is not req'd, but I can't find this now as I'm beginning...
    Thoughts?
     
    #18 JohnStef, Mar 3, 2018
    Last edited: Mar 3, 2018
  19. zsolar

    zsolar New Member

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    the wiper motor does need to come out, but it will come out with the cowl assembly. I just meant there is no reason to unbolt the motor from the cowl.
     
  20. JohnStef

    JohnStef Member

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    I am such an amateur, I think I'll fix the 1/2 shaft before ... Please don't tell my wife! She thinks I'm a good mechanic.

    For the record, about 3 weeks ago, the car made a little bit more noise than usual, deep exhaust kind of sound. There is a good chance the 1/2 shaft was self destructing, making this noise. Then the snap and rattle sounds.

    Lesson learned, look around 1st, don't assume anything.

    John
     

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    #20 JohnStef, Mar 3, 2018
    Last edited: Mar 3, 2018
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