I have a 2500 05, QC/SB/auto 4x4. Right around 70-85 mph, 2100-2500 rpm on the tach the Cummins really starts to drone in the frame of the truck. It's not the typical 70 mph vibe drivetrain issue, my frt end is smooth as glass. This is just an annoying drone due to engine rpm and a very stiff frame perhaps. Any fixes? I doubt it.