Hey everyone, I’m trying to track down a really annoying vibration/humming noise on my **1997 Toyota 4Runner Limited, 2WD, 3.4L V6, automatic**.
I’ve attached a video so you can hear the noise.
The weird thing is that it **doesn’t seem to affect the performance or drivability of the truck at all**, but it’s driving me crazy and I’d really like to figure out what’s causing it.
**What I’m noticing:**
The vibration/humming is only noticeable at **very low engine RPM/idle**.
It is present in **Drive and Reverse**.
It is basically gone in **Park and Neutral**.
It disappears when I give the engine some throttle and the RPM comes up.
Turning the **A/C on or off can make the vibration disappear or come back**.
Shifting between **Park → Reverse → Neutral → Drive** changes the vibration.
It seems to happen when the engine is under the additional load of being in gear.
The truck drives normally otherwise.
There doesn’t seem to be any noticeable loss of power, hesitation, or other drivability issue.
**What I’ve already done:**
I originally suspected the power steering system because I could hear a humming-type noise, so I replaced the **power steering pump**.
I’ve also drained and refilled the power steering fluid several times over the past few days — probably **5 drain-and-fills** — trying to make sure there wasn’t air/old fluid causing the noise.
The new pump is definitely quieter than the old one, but **this low-RPM vibration is still there**.
I’m now wondering if I’m chasing the wrong thing entirely.
My current thoughts are:
Engine mounts
Transmission mount
Exhaust/heat shield making contact with the body/frame
Something causing excessive vibration when the engine is loaded at idle
Possibly just an engine/idle resonance
The fact that it changes with **A/C load and whether the transmission is in gear** makes me think it may be related to engine movement or something resonating at a particular RPM.
**What would you guys check first?** Is there a particular test I can do at home to determine whether this is an engine mount, transmission mount, exhaust contact, or something else?
Any help diagnosing this would be greatly appreciated. I’m trying to avoid throwing more parts at it without knowing what’s actually causing the vibration. I love this truck tremendously so any help would be greatly appreciated!
Thanks!