Buzzing noise 1800 rpm in drive

[Culpeper]

I've got a wierd buzzing noise resonating through the left dash right at 1800 RPMs while driving. I can't hear the noise with the vehicle in Park. I'm concerned that it may be the motor but the buzzing sound is constant unless driving on a bumpy road, in which case, it tends to be affected by the bumps, which makes me suspect something might just be loose. I can't hear the noise with the windows down. The vehicle has 140k miles on it and a complete history of preventive maintenance through Toyota for it's entire life. I have taken it to the Dealer twice and not surprising they can't determine the cause or don't want to. It is a 1990 model 4R with V6. The noise is not present below or above 1800 RPMs.

 

[Culpeper]

Solution

For further reference.

Resolved the noise I was describing;

Using chassis ears pinned down the noise to the left fender well. Insulated/tightened down air filter box, mount point from fender to radiator, alternator wiring harness. The noise was harmonic meaning at a certain rpm range under load it would create a vibration through the left fender well. The noise/vibration would travel this area of the chassis like a bell and reverberate behind the instrument cluster inside the cab. So much so that to the naked ear you could swear the problem was with the dash or instrument cluster area.

I appreciate nobody spamming this thread with standard BS like, "you sure there isn't an 18 wheeler going by when ya hear it!"

 

[jhinderliter]

does your left side mirror vibrate as well? can you feel the vibration in the steering wheel?

 

[Culpeper]

No, my problem was just resonating noise caused by loose components under the hood. It was a bitch to find until a set of electronic chasis ears were used.

 

[AznKlique]

My 4Runner seems to buzz like crazy too, only when its cold outside. The buzzing would start at around 20mph and then the buzzing would go nuts when the car goes faster. Could it be the odometer cable?

 

[Culpeper]

My 4Runner seems to buzz like crazy too, only when its cold outside. The buzzing would start at around 20mph and then the buzzing would go nuts when the car goes faster. Could it be the odometer cable?

Possibly. You can disconnect it at the transmission to see if that is it or not.

 

[AznKlique]

Possibly. You can disconnect it at the transmission to see if that is it or not.

Uhhh...no thank you. I dont wanna break anything...

 

[Culpeper]

Final Solution on my vehicle

All the other things we did above only masked the real problem. Turned out it was the alternator that was the source of the noise. Replaced the alternator when needed and the noise was gone. Problem: noisy alternator.


I should have posted this a long time ago.