Bad Vibration between 2400 and 2800 RMP

[BigRedWeather]

For the first time tonight I had the guts to take my truck over 2400 RPM and found out that it looses the vibration after 2800.

Here is the link to my previous post on this: http://www.oilburners.net/forums/showthread.php?p=377678#post377678

Any insights as to the cause would be welcome.


BigRedWeather