Willi

[Willi]

Hey guys I have an 08 cummins and when I have a load on it and go between 45-55 mph when the engine is at a certain rpm usually lower rpm it vibrates any faster or slower it's smooth any suggestions?

 

[NWRQC]

Welcome to the site.
Can you provide any more info? Where does it seem that the vibration is coming from (engine, trans, suspension, etc) Is it in any gear or a specific gear?