Intermittent But Troubling Noise When Accelerating

I'm getting an odd noise that I've never heard on this or my previous Tacoma. It's sort of a whirring or grinding sound. It occurs only when accelerating - never when idling, coasting, or braking. Tends to be worst when first accelerating (0-20 mph). The noise is also intermittent - it doesn't happen all the time when accelerating and some days it seems to barely happen at all. As best I can tell, it sounds like it's coming from the passenger side of the engine.

No noticeable change in handling or acceleration performance, just noise.

2013 Tacoma automatic 4-cylinder, well-maintained, 115K miles.

Any ideas what might be going on?

 

Driveline rubbing on something only when flexing under acceleration? Is the noise coming from the front or the rear?

 

As best I can tell, from the front.

 

I just had a similar issue with an intermittent screeching noise. Happened when the engine was around 1500-2000 RPM. Turned out to be a loose heat shield above the catalytic converter and/or the clamshell cover around the cat itself.

The forward most mounting hole of the heat shield had corroded away around the mounting nut so it was free to wiggle and vibrate. Luckily the stud and nut weren't too rusted so I was able to get the nut off and add a fender washer.


I noticed the bolts holding the clamshell cover around the cat were all rusted and one was pretty much gone making that corner loose. Rather than trying to remove the rusted hardware and replace it, I just added a stainless steel hose clamp around it to sinch it snuggly back together.


Not sure which one solved the issue, but no more noise.

 

I would guess u-joints. Jack up the back end, get the tires off the ground, chock the fronts so it won't roll. Then, put it in neutral without the parking brake so there's no bind on the drive shaft.
Get under it and twist, wiggle, and shake the drive shaft near the u-joints. You shouldn't have any movement or looseness in the joint.
The fact that it's happening under load makes me suspect this.

 

My catalytic converter was replaced about six months ago (someone stole it overnight!) and it's possible some part of the replacement wasn't tightened enough and has loosened. I will take a look.