One common problem I’m familiar with is called “ frame beaming” (TSB 1844688). It’s a beam shake vibration that is usually felt in the seat and occurs between 40-60 mph. Severity of the shake may vary from vehicle to vehicle. The diagnostic procedure says to place 200-500 lbs in the bed and if the shake goes away, it’s “beam shake”. The TSB further states it’s a characteristic of the vehicle and that there is no fix (for the 2500/3500HD’s).
On my 03 crew cab I get a slight bounce type vibration at approximately 45mph when the bed is unloaded.. In the winter I run with four 80lb sand bags in the bed and the vibration is gone.
Bill
03 2500HD D/A CC/SB/4WD,OilGuard, MegaFilter,LiftPump/PreFilter, Bilsteins,RetraxRollTop,J&J Boards,Coolant Filter,AlliDeepPan,FastIdle,AllHeadLightsOn,
98 K3500 6.5,SOLD