I am driving a '98 Tacoma with the 2.7 L engine and 4wd. She has 289k mi and for the most part has been a champ. Last year she started to show her age and had to have the head gasket and ac replaced. I was too busy to do the work myself and let the auto mechanic class at the school where I teach work on it. Everything has been good with the repairs so far. Last week I was in some rough traffic and I downshifted too agressively. Ever since then I have been getting a loud squelch/squeal/grind noise on occasion when I am backing up (very common), going over speed bumps (occasionally) and downshifting (rarely). It doesn't do it when I am idling which makes it hard for me to listen to it. It feels like when I am reversing I am loosing some power, but that could just be in my head. Checked all the belts and they seem to be in good order and properly tightened. Any ideas??

 

Check for clearance between your fan and shroud or any evidence of the two making contact.

 

Motor mount?

 

The fan and shroud both look like they are in good order. Shroud is securely mounted with no signs of contact with fan and all the blades of the fan are firmly attached. Blade tips don't show any recent contact with anything. Had checked it before and just went out and gave it a second look. Nothing.

 

It appears to be firmly mounted. I don't notice any play when I aggressively rock it back and forth. Just moves the whole truck. Also don't notice any loose or missing mounting bolts.

 

would you mind posting your location? maybe another member in your area could take a listen or you could make a video/recording of the sound and post it.
Also tell us WHERE the noise seems to be coming from.
Another possibility is from the clutch, stick shift right? "downshifted aggressively".
There are springs mounted around the clutch disc to help soften the engagement, you may have broken one or collapsed all of them allowing them to rattle.

 

So here is a video that seems to get the sound pretty well. It makes the noise twice as I am reversing into my drive.

Sound seems to be coming from the front of the engine compartment. But can’t tell if left, right or center.

And I am located in Austin TX.

 

Sounds like a throw out bearing, IMO of course. When mine went out it would be the same squealing grinding noise but in shorter intervals.

Was the clutch ever replaced?

 

Disco, I think the clutch is still original, and unless I am backing up the times I hear the noise are usually very short. Anyone else second the opinion on it being a throw out bearing??

 

I haven't been able to listen to your recording yet, company firewall blocked it. If it is your throwout bearing the noise should change (go away or get louder) if you push the clutch pedal just enough to put a little pressure on it, not slip the clutch.