Wheel bearings make a rattling/scraping sound when you turn. You can check them by lifting the car off the ground and grabbing the tire and trying to shake it off, if you feel any play whatsoever then it's time to get new wheel bearings, or new hubs. Or keep driving and wait until your bearing seizes and your wheel falls off, up to you.

The TSB says 220ft/lbs but in reality you want to tighten to 220ft/lbs + 60 degrees. The nut is six sided and 360/6 = 60, so one side of the nut over from the location you tightened to 220 to would give you enough torque. To take off the axle nut, remove the little dent on the nut with a dull chisel and use the longest breaker bar you can find, or if you have a 1/2" impact gun you can use that, if you have a 3/4" one even better. I believe you'll need a 36mm socket. When re-installing the axle nut grease the face of the nut, not the threads nor the mounting surface, just the face of it, otherwise your torque setting is useless. Finally when you tighten the nut, put the little dent on the nut, this will help keeping it from backing out.

Have you checked your differential mounts? Once they go pop they'll cause vibrations under acceleration. It's easy to see if they're bad because you will see dried up liquid from them. It's usually the left one that goes.

Edit: I just saw your video, I don't know what it is but it doesn't sound good, it could be suspension bushings, or loose subframe bolts. Get it checked out ASAP!

 

Got underneath the car this morning. Bushings looked fine. I checked all of the subframe bolts. I had one loose one on the rear passenger side (tightened it). The rest were tight.

 

So any difference now?

 

I haven't driven the car yet, but I doubt that one slightly loose bolt would cause the problems I'm experiencing. We'll see I guess. I'm still entertaining other options.

 

That really won't tell you much.

The proper way to test bearings is with a dial gauge looking for less than 0.05 MM end play... even crap bearings don't give enough to feel it shaking the tire. Most failures are found because of the sounds they make once hot and rolling at 20 - 35 mph.

 

Well I'm just assuming that OP doesn't have a shop with professional tools like dial gauges. .05 mm is about the space between these two lines -- if there's less end play than that I don't think you have a bearing problem , maybe more than .05" or the space between || ok.

 

Another plot twist... The vibration phenomenon is much worse when the car is hot than when it is cold.

 

You sure your diff mounts are ok?

 

They looked ok, though I didn't' check the torque on the bolts. Looks like I've got one more thing to do.

 

Revisiting this issue. All bolts are tight. I also pulled the driver's side axle and expected the joints a few days ago. The axle is perfect.

At that point I gave up trouble shooting the issue myself and took the car to the Honda dealership. Both a technician and shop foreman drove the car and said the vibration was "very strange. They asked me about my suspension mods. I told them what I had (mild springs, shocks, and swaybar upgrade), and mentioned I didn't think any of that could be causing the vibration. They apparently agreed and dug a little deeper. Today they called me suggesting a "differential service" with new fluid. I told them that the fluid had been changed 5 months ago and that didn't effect the problem at all.

So after two days of troubleshooting they are stumped.

With the axle ruled out, the only thing left I can think of would be that a mechanical component of the differential has failed. If any of you drivetrain gurus have any specific guesses as to what this might be, I would greatly appreciate it.