I posted this in the Tech/Misc forum but since it might be transmission related I thought I'd ask here.

Original thread here: https://honda-tech.com/forums/tech-misc-15/so-what-might-noise-when-throttle-2915450/

For the past couple of years I've been hearing this low-pitched noise when on the throttle, mainly in 3rd-5th gears, mainly between 35-55 mph. It's kind of a low-pitched wawawawawawawawawa, and goes away as soon as I close the throttle.

It seems like the frequency of the "wawah's" changes with speed. I guess that pretty much means it's transmission-related, right? I believe the sound is more audible in higher gears and lower (than highway) speeds due to less engine sound drowning it out. I can't hear it in lower gears and higher RPM, and at higher road speeds, I believe because of engine and road noise.

Car drives and shifts fine, always has. It's about to turn 300K miles on the original engine and transmission, but like I said everything feels fine when driving, still can get around 30 mpg average on my daily commute to and from work.

I do not feel any bucking when closing the throttle, except maybe in 1st gear going very slow, below 1,000 RPM, but that should be normal anyway I think. I've been running GM Synchromesh Friction Modified for the past nearly 150K miles, and have about 25K miles on the current fill. Rear engine mount and both front torque mounts are new OEM, barely more than 2 years old. I do not hear any odd sounds with clutch engaged vs. disengaged. This only occurs with engine under load (throttle open) but I'm thinking transmission since the sound changes with road speed.

In the other thread TunerN00b mentioned transmission backlash, which surprisingly is something I haven't heard of before, and am not sure how to check it.

Any ideas or suggestions would be greatly appreciated. I doubt I would be able to make any kind of video or recording of the sound, as the only equipment I have (iPhone and Canon point-n-shoot camera) probably wouldn't be able to pick up this sound over the other engine, road, and wind noises in the car.

 

Has that transmission ever been apart before Patrick? If it's not making noise with the clutch out in neutral i'd lean towards diff bearings if anything. Normally bad main and countershaft bearing make noise in neutral and the lower gears and get quieter as you get up into 4th and 5th.

 

Nope, have never opened the transmission up. Never opened the engine up either (removed head). I'm hoping I won't have to.

There are no odd noises while in neutral, and no change in the normal engine idle sounds when disengaging and engaging the clutch while stopped.

 

Could it be anything suspension related? Wheel bearings? I hope not, as my front wheel bearings are only 4 years old at the most I think, maybe 50K on them. Rear wheel bearings are still original but don't think noise from them would go away when closing the throttle.

It's almost like the same conditions as when inner CV joints go bad (vibration at certain speed, only under load) but I'm not feeling any excessive vibrations our of the ordinary.