Timing chain - parts that wear

[pdgizwiz]

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

[Jonny]

From my '91 with 298K miles

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

13048

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

13049

13050

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

13051

Slipper is a bit of a mess too...

13052

13053

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

13054

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).

13055

[TCR10]

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?