Help noise!!!!

[Lherrlinger]

Hey guys not sure what this noise is.... it is a vibrating noise that only comes at 70 mph till about 75 but above and below it does not happen it’s kind of a ruff humming buuuuur noise was wondering if it was just wind or drivetrain related. Any advice would help!!! It’s a 6 window short bus with an 03 e450 7.3

 

[Tango-SKO]

Oh NO! Not another Harmonic Noise Mystery!


But seriously...these can be a nightmare to track down.



They can be engine related (harmonic balencer, fan, belts. etc.).


They can be driveline related (drive shaft, tires, etc.)


They can be body/chassis related (sheetmetal can also resonate at certain frequencies)...


Lots of possibilities. Helps to have a partner when trying to track it down. Maybe even with a mechanics stethoscope to isolate (or at least get close to) the source.


No easy answer. Best of luck and let us know what you discover.

 

[joeblack5]

Try to take the strain of the drive train by getting up to 75 and then let go of the throttle a little, not all the way, so do not brake on the engine. Listen if the sounds is gone from 75 to 70. If not gone then check tires, bearings. If gone then check the u-joints, drive shaft balance, differential wear and play


If gone you can try to coast at between 75 and 70 and put the tranny in neutral and bring the engine back up to the same rpm and listen if the noise comes back to check for harmonic vibration that is engine / fan related


Little tricky to put it in neutral because i would not put it back in gear from neutral while driving faster then 5 mph. All depending on the action of your transmission but you want to avoid that your transmission is selecting first gear while you are still doing 60Mph. so beware


Good luck J