Nissan Repair: 97 Hardbody dash noise/vibration, vibration noise, noise vibration

Question
Here are the basics.  I picked the pickup up about 2 weeks ago.  While driving there is a rattle/vibration/noise coming from the dash about the middle area when the engine reaches about 3500 rpms and then goes away if you let it get a little higher, around 4000 rpms.  This noise only happens when the engine gets around those rpms, whether or not your driving.  I was curious if you have come across this before.  Any help would be appreciated.  Thanks in advance.

Answer
Hi Steven -

Unfortunately there could be a lot of items that could cause this noise at a particular speed. Most commonly it is the A/C ductwork, in the area, or the plastic dash housing throughout the vehicle. If it is coming from outside, I say it is the interior lining of the exhaust pipe, which is common. Are you sure it is from the interior? If so, then I would say a process of elimination. I usually have someone drive the car while I go and look for the sound.

Hope this helps, and hope you find it -
aloha
calvin