I went on mission to finally fix the idler pulley (s) that have been whining ever since I went to Pine Barrens.

For those of you that want to tackle the project I can say it’s pretty frekin simple. The hardest part was finding stores that carried the pulleys without having to special order them.

You need two of these.
Dayco 89158 Idler Pulley : Amazon.com : Automotive
And one of these.
Amazon.com: Dayco 89169 Idler Pulley: Automotive

Start by attaching a socket with a long handled ratchet to the tensioner and removing the belt. (or just let it dangle)
All of the pulleys came off pretty easily. Put your new pulleys on and route your belt. I found it easiest to route the belt with everything except the power steering. Then using a long handled socket to move the tensioner until you get the belt around the power steering pulley.
Removal / Replacement probably took 45 min. Tracking down the parts took 3 hrs. I figured I’d save you all that trouble.
These pulleys I linked from Amazon are the exact parts I got at the stores. They were direct fit to existing hardware.

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How did you figure out that you needed to replace your idler pulleys?

Yes, the job is quite simple.

The only trick to remember is which pulley is reverse threaded - I also did the tensioner pulley (I see you didn't do that one).

When I bought my 2006 4Runner (115K miles), the engine sounded like an old textile mill running pull capacity with the all squealing and squeaking coming from the front of the engine. After replacement of the three pulleys, it absolutely purrs.

I did this job on my 2001 Lexus GS430 at about the same mileage after it too start sounding like 1800's textile factory.

Take the belt off. Grab pulley, twist side to side. If its grinding replace it. If its smooth spin it. Does it spin freely? If it does, its good to go.

When I started my truck you could hear them bearings went bad it made an awful racket.

I actually got my belt and both pulleys replaced by a local Toyota shop (and got ripped off) and will probably do it myself next time. Works and sounds fine now.

is there one pulley that generally goes out before the others? i guess what i'm asking is whether i should replace them all at once or try one by one until the awful sound stops.

Save yourself the hassle, and just replace them all while you're in there.

any input on OEM vs. aftermarket? seems like most people use the gates 36173 & 36174 ($35 & $39 each on rockauto, respectively, pushing $150 for all four), but i have a friend who works for a toyota dealership and gets me buddy prices on everything i need. OEM pullies are around $55 & 65 on amazon. i don't mind paying a little extra if gates are better, but if OEM is the way to go that'd be nice because of the discount.

Hey, I have a whine from my 97 V6 3.4L engine (188k miles). I had the water pump and timing belt replaced, along with all the belts about a month ago. The engine whines in neutral as well as drive, hot or cold, at idle and 20 mph, and the whine gets more high pitched with rpms. When I turn the wheel side to side I can hear the sound swinging, but it's also there when I'm not turning the wheel.

I thought it was the power steering pump at first, but after flushing the power steering fluid last night there is no change what so ever. My guess now is the idler pulley. Does this makes sense to you guys? I've also been thinking about the alternator, but have yet to experience any issues with the battery. The sound is most definitely a whine, not a typical belt squeak.. Any suggestions are highly appreciated!

It sounds like the power steering pump going bad to me, get yourself a mechanic's stereoscope so you can pinpoint exactly where the whine is coming from, just be careful using it around pulleys and the belts, you can get one at most any auto parts store for $5 and up, most inexpensive ones are around $10 or so.

I would not classify my failing idler bearings as a whine. It was a high pitched chirp (like a bird) that increased and decreased with RPM. Only prevalent on cold starts--and went away after a few minutes. I suspect your whine is a different problem.

Hey, thanks for the suggestion! Went out and got a stethoscope today though, sound was coming from the alternator bearings. Replaced it and problem solved!

So the OP does not mention a pully being reverse threaded at all. Is the accurate? Which pully is reverse threaded?

The tensioner.

thanks to lots of research on thhis forum, TW and FJ forums, i finally changed mine last weekend. i ended up buying OEM upper and lowers and just replacing the bearing in my tensioner. problem solved! and it was all so easy.