Tires: Vibration, ford f150 supercab, rotating tires

Question
Hi Barry,

I have a 2002 Ford F150 SuperCab. 90,000 miles. Over the last 2 years I have developed a vibration that starts while traveling at about 40mph and worsening at highway speeds. It feels like the seat is vibrating sort of a cyclic side to side motion. I have take the driveshaft to a driveline shop and had the driveshaft balanced. Today a mechanic told me that it might be the tires. The vibration was there before the tires were replaced about 1 year ago. I have the BFGoodrich Long Trail TA on the truck. The tires have not abnormal wear. He suggested that I have them on truck spin balanced. Iy is hard to find a shop that still does that.  I have swapped tires front front to rear without and change in this annoying vibration. He also suggested finding another similar truck and swap tires and see if the problem continues.I have heard of Road Force
balancing. Would you have any suggestions?

Thanks
John

Answer
John,

I don't think this is tire related.  The speed is too slow.  Normally wheel end vibrations are in the 50 to 70 mph range.  Plus, changing and rotating tires should have made some difference.

I would suggest you look at U joints and pinion angles.