Noise description: droning or buzzing noise resonating through the instrument cluster. Already checked the speedo cable and gears and shut off all instrumentation to the dash with no success in troubleshooting.

In Drive, I can hold the accelaration steady at 1900 RPM and make the noise occur until it goes away after about a minute. When accelerating through the 1700 - 2000 RPM range it will make the noise as the tachometer goes through this range. So, on heavy accelaration the noise is just a blip as it quickly passes through this range.

Also, I can duplicate the noise in Park by reving the engine to 2800 RPMs. Or quickly reving from a normal idle sort of like Vrooooom Vrooooom Vroooom and you can make out the noise under the normal engine noise.

4Runner is 1990 model with V6 auto transmission.

The noise doesn't seem to be getting worse over time (approx. 3000 miles).

Thank you

5qcqv

 

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!"

 

Man, I don't have a high post count so I was just going through them. Much later I found out the problem was related to the alternator. It eventually needed to be replaced and the noise was gone for good. So, I'm just following up. All that stuff above was just a band-aid. Thanks.