my truck shakes at high-way speed. is it the tires? or could a rim be bent?

could be any of what you posted,or a bad u joint in driveshaft.

A failed u-joint will not cause the vehicle to shake in the manner you described. I would have a mechanic inspect the front steering and suspension components to verify they dont have undesired play in any joint causing uneven tire wear/shake. Even with a bent rim the wheel/tire assembly can most times be balanced to allow a smooth ride. Also, if the tire shop is reputable they should be able to perform a road force variance balance which would tell you if there is an underlying issue with the soundness of the tires. How much life is remaining?

you are very wrong on the u joint.

Kudos Jon, you were bright enough to realize that a u-joint problem isnt speed specific. Some people aren't that bright.

A bad u joint makes a clunking sound when the car is put into gear while at a dead stop. drivetrain problems are not speed specific, they are consistent with engine RPM. Keep hanging in there, you'll learn all this someday.

A u joint is speed sensitive. It goes around with the back tires… that said, my bad vibration was a faulty u joint. At 35mph it would start to shake and around 65 the harmonic balance of the out of balance driveshaft would take over and be not as bad.

Missed the fact the transmission is engaged at 'highway speed' Jason.

2001 Excursion 4x4, 201000 miles. I have had the drive shaft, slip yoke, replaced and balanced, tires are new and have been force balanced, yet I still have a 35 and 65 mph vibration. Thoughts?