Thanks Punchy, but I don't know about being a genius!
VTGrad, it could be a balance issue, but it should be more of a constant vibration. What tire brand are you running? Some of these commercial tires just will not balance no matter if they are trued. Also, I have heard of people having balancing issues that was caused by the tires not being seated properly. I personlly think a computerized spin balance with weights is the best balance you can get. A local big rig tire shop should be able to spin balance your tires. It really though doen't sound like a balance problem.
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2006 DODGE RAM 3500 - Silver, Reg. Cab, 4x4, Dually, 6spd, Quadzilla X2 Race Module, CFM+ Intake, AEM Workhorse Intake, Banks Monster Dual Exhaust, MBRP Cat. Delete Pipe, Isspro Gauges, Air Horns, ReadyLift Leveling Kit, 22.5" Alcoas, 255/70 Sumitomos.