The Nissan Path

I have a 2007 Pathfinder just over 200k and I'm getting a fairly loud humming/buzzing only at about 2500 rpm. I almost exclusively hear it on the highway around 80mph, though it occasionally happens (a little quieter) when accelerating sharply and the automatic transmission upshifts through the lower gears. It's always the same pitch, not particularly high or low; it almost sounds like groaning/friction and goes away whenever I give more gas or let up on the throttle. I don't get the noise revving the engine when not in gear. Tough to tell exactly where it's coming from. I wondered about a heat shield resonating at a certain frequency, but I do feel a light vibration through the gear stick when I hear it (uh oh).

I recently changed engine oil myself, and a mechanic did transmission fluid and a bad wheel bearing not too long ago. Before I investigate further, any ideas what this could be? Certainly wouldn't be surprised if it's transmission related, though thankfully there are no telltale signs of the radiator leaking coolant into the trans. fluid (strawberry milkshake of death). Everything seems to be running pretty well otherwise but this noise is annoying and elusive!

NoSo17 wrote: ↑

Sun Nov 27, 2022 12:44 pm

I have a 2007 Pathfinder just over 200k and I'm getting a fairly loud humming/buzzing only at about 2500 rpm. I almost exclusively hear it on the highway around 80mph, though it occasionally happens (a little quieter) when accelerating sharply and the automatic transmission upshifts through the lower gears. It's always the same pitch, not particularly high or low; it almost sounds like groaning/friction and goes away whenever I give more gas or let up on the throttle. I don't get the noise revving the engine when not in gear. Tough to tell exactly where it's coming from. I wondered about a heat shield resonating at a certain frequency, but I do feel a light vibration through the gear stick when I hear it (uh oh).

I recently changed engine oil myself, and a mechanic did transmission fluid and a bad wheel bearing not too long ago. Before I investigate further, any ideas what this could be? Certainly wouldn't be surprised if it's transmission related, though thankfully there are no telltale signs of the radiator leaking coolant into the trans. fluid (strawberry milkshake of death). Everything seems to be running pretty well otherwise but this noise is annoying and elusive!

hello Welcome to TheNissanPath your new home away from home!

First things first (and these are likely completely unrelated with the question that brought you here, but please bear with me)

your last paragraph makes me believe 2 things:
a) you have not either changed the radiator ye,t or done the ATF bypass. and
b) you may consider "checking for SMOD" to be a preventative action.

First allow me adress b)
When you see a symptom of SMOD in the fluid even if the trans still works fine it is already irrevocably ruined in 90% or more of all cases.
Any mixing of the fluids destroys key elements of your (otherwise quite stout) transmission within a couple of days
The ECU ( rust) and the clutchpacks.

So my recommendation is before you even sort out the noise please read this thread it talks about this in great nuance and what you might do at very low cost to you.
about-to-be-new-owner-radiator-question-t17198.html

As for the noise itself those Things can be difficult to track down. I had some weird noises form loose heatshields and or loose exhaust hangers in that general rpm range before but not having heard the noise ( can you post it up?) its hard to judge form here.
My advice would be to spend some quality time under the truck and to look for loose exhaust hangers and/or heat shields.
My vehicle is at 186,000 miles and makes no funny noises but it takes some vigilance to keep it that way.

There are mechanically smarter people than me on this board so you should get some more input soon.

Hard to say without more info on the sound. I have in the past (on my 73 BMW bavaria) had drive shaft vibrate at a specific speed. Could also be related to any of the engine or transmission mounts changing angles etc. but there really are a lot of things it could be.

Maybe check the belt tensioner pulley, AC compressor, alternator etc. on the serpentine belt.

If it makes the noise at the same RPM in any gear then you can eliminate the drivetrain, it has to be from the engine or something directly attached. If not, since you know what RPM and gear the noise occurs at, using a recording along with an audio analysis or graphing app will tell you the frequency of the noise. You can then figure out from the gear ratios which part of the drivetrain is causing it.

@ 2500 rpm on your driveway - any noise?

Appears at the same RPM and speed, could be wheel bearing noise.
Humming, etc appears on the highway and the truck is travelling at very consistent wheel rotation at RPMs

Easy test is the pepper grinder to find out.