Timing chain - parts that wear

I've had several 2TZFE engines apart now, most with 250k + miles on them. All show wear and degradation of the plastic/rubber portions of the chain guides. None have shown appreciable wear on the metal parts (chain and sprockets). I've replaced the wearing parts with kits purchased off of ebay, and lucked out until recently. The last kit I bought contained guide parts that were so out of whack dimensionally that they were unusable. Had I used them, there's no telling what kind of issues I'd have had. I buckled down and bought OEM parts, which are - of course - perfect. More expensive, yes. Once again, efforts to save a few bucks have run aground.
These are simple parts that one would think even a dirt-floor factory could get right all the time, but from my small sample can only do so two out of three times. I've never used the metal parts in these kits, preferring broken-in but still-in-spec OEM parts to new parts of nebulous integrity.
The wearing parts are composed of metal pieces that have a soft plastic molded onto them where the chain rides. I guess their tooling and/or process fails to control the alignment between the metal piece and the cavity of the mold. Anyway, lesson learned... I'll go OEM from here on.

Part numbers for 2TZFE (non-S/C):
13559-75011 Slipper, Chain Tensioner - This is the swinging part on the slack side of the chain
13561-76010 Damper, Chain Vibration - This is the fixed part on the tension side of the chain

From my '91 with 298K miles

Slipper, top. Damper, bottom. Little gremlins, middle.

Attachment 13048

lots of bits of plastic flaking off the back of the damper

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Front of damper has considerable wear and broken-off bits...

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Slipper is a bit of a mess too...

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These pieces were just chillin' in nooks and crannies inside the timing cover.

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My '85 Toyota pickup had similar broken/worn plastic parts when I did its head gasket at 220K miles.

This damper for the number 2 timing chain is only a little worn. I might leave it, esp since, though it is clearly detachable via 2 bolts, it only seems to be available as an assembly with the idler gear (for beaucoup bucks).

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Thank you both for this very worthwhile thread. With the age of our Previas and the nature of these parts I imagine they should be replaced, but it appears that the engine must be removed to do the job.
Are there any noticeable symptoms from worn out or degraded slippers and dampers?

Some info for 2025....

It appears that the timing chain Slipper and Damper are both no longer available from Toyota. Some 3rd party OEM parts websites still have the Slipper listed, but in reality, unless they have it on the shelf (v. unlikely) it is "backordered with no delivery date". This to me means it's a precursor to "product no longer available".

Rock Auto has few options, with some of their past offerings apparently unavailable also. Perhaps these parts are going to be rather hard to acquire soon?

I ended up buying the S.A.Gear slipper and damper from Rock Auto. Made in Taiwan. They do fit, so S.A.Gear does not seem to have the qc problem which pdgizwiz had (above) with his aftermarket parts. Again, sample of one.

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Here are the old and new slippers side by side.

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The "collar" thing sticks out further on the S.A. Gear part. It seems like it is not pressed in quite far enough (see pics below). Fixable.
One thing which surprises me a little is that the Toyota bolt which holds the slipper to the engine has a washer OD which is slightly smaller in diameter than the collar OD. So the collar is held in place securely but the main slipper part is dependent on the press fit onto the collar to keep it in place. I'm sure it's fine but it seems like a larger washer would have been good insurance so that at least there was no way for the slipper part to "slip" axially forward.

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Here are the old (bottom) and new dampers...

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The plastic co-molding on the S.A. Gear part is a lot rougher. I'll probably just trim the flappy bits off with a knife and hope for the best. These areas are on the back of the damper, not the chain surface, but they're sure to flake off in time.

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The tip of the old Toyota damper, with my thumb on it, is metal with no plastic coating. The S.A.Gear damper's tip, to which I'm giving the middle finger, is coated and you can see what has already happened to it in handling and shipping. It'll get trimmed off too.

Attachment 13470

At least the new one doesn't look like this (after 298K miles)...

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If anyone knows a source for the original Toyota parts I'd love to hear so that I can get spares for my other Previa.