Update on Gen 3 issues

donzoh1 · Aug 28, 2022

ASRDogman said: ↑

$100?????
Are you certain it's the correct one? That price is pretty low.
Are they used? Which would not be worth the risk.
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I saw some in the 300 range (I think aftermarket) and saw some dealer parts in the 1,000 range. Obviously, I'm not doing the dealer thing, assuming that price is correct. I think this part failed because of underlying misfire issues (as Chap said) and if the ICE is dialed in, it's not likely to fail again. It's true though that getting this part in and out is a mess so any new failure is going to be a problem, whether it's based on a defective replacement part or an OEM part that's destroyed by ongoing misfires.

donzoh1 · Aug 28, 2022

ChapmanF said: ↑

The disc in the damper does indeed look like a typical clutch disc, and like one of those, it has a couple jobs that are related but different:

You can see the friction material around the edge, and the coil springs arranged around the center.

The friction edge is what's clamped between the pressure plate and the engine flywheel. In another car's clutch, the pressure plate could be released by a pedal, but in the Prius it's just permanently bolted down. There is enough friction there to carry all the torque the engine and transmission are built to normally handle. It will only ever slip if something happens to put higher torque than that on the components, maybe a bad engine stumble while the car has forward momentum, or if something in the engine or transmission seizes up while the other is turning.

That slipping action doesn't make any banging noise or shakes. People in cars with clutches don't get banging noises as they put in or let out the clutch.

The coil springs around the center have the job of taking up small bounces between the motions of the engine shaft and transmission shaft. The engine really supplies power in four bounces every two revolutions, and the car's ECUs do their best to try to spin the electric MGs in synchronization with that, but perfection is elusive, especially if the engine might be running a little roughly, a tire hits a pothole, etc.

The disc is really two discs with a common center. The outside friction edge is on one disc, the center transmission splines are on the other. The coil springs sit in cutouts between the two discs, so that one can bounce a little ahead or behind the other, compressing the springs.

This normally doesn't make any noise either, but if there is a big enough bounce to compress the springs completely, that'll make a metal-to-metal clank. If there is a reason, like a routinely misfiring engine. to make a lot of bounces that big, that'll be a lot of clanks.

If that continues long enough, say an engine misfiring issue that doesn't get fixed, eventually those coil springs will fail. You can reach into the bell housing through the little hand opening and find spring fragments in the bottom. That leaves nothing at all in those openings in the disc, and so the two disc portions are then free to clank ahead and behind each other by the full width of the spring cutouts with nothing absorbing the bounce, and that is a really awful racket.
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donzoh1 · Aug 28, 2022

I did replace plugs and coil packs although not sure those were really problematic. There was a code for the water pump and I'm thinking an overheat situation may have lead to misfire which led to input damper failure? Right now, it has no codes and I'm thinking it should be driven for a bit to make sure they don't come back before changing the damper. I don't want to change that if the underlying issue wasn't resolved. Would that damage anything or is it just noise that must be put up with.

ChapmanF · Aug 29, 2022

I wouldn't want to drive too far with a springless damper ... there will be very high instant torques involved every time those discs hit the ends of their travel, unsprung.

Somebody a few years ago made a "WTB" post with a picture of the damper you can still see the broken-off end of the transmission input shaft in. Ouch!

On the other hand, you can maybe do a risk analysis involving how far you're planning to test drive it with an unsprung damper, compared to how far it was probably already driven that way before being brought to you.

donzoh1 · Aug 29, 2022

ChapmanF said: ↑

I wouldn't want to drive too far with a springless damper ... there will be very high instant torques involved every time those discs hit the ends of their travel, unsprung.

Somebody a few years ago made a "WTB" post with a picture of the damper you can still see the broken-off end of the transmission input shaft in. Ouch!

On the other hand, you can maybe do a risk analysis involving how far you're planning to test drive it with an unsprung damper, compared to how far it was probably already driven that way before being brought to you.
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ooops!

ChapmanF · Aug 29, 2022

On the bright side, the clattering racket surely stopped at that point.

donzoh1 · Aug 30, 2022

ChapmanF said: ↑

On the bright side, the clattering racket surely stopped at that point.
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Yes, that would bring the clattering to a stop. I'm guessing the driver didn't see it as a comprehensive solution though.

Update on Gen 3 issues

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