Ford Repair: Rear Vibration, monroe sensatrac shocks, ford f150 supercab

Question
QUESTION: Hi Chris, Thanks for taking the time to answer my question. I own a 2002 Ford F150 Supercab, 4.6 l engine 2 wheel drive, short bed. It has 84,000 miles. It has had a vibration that is felt in the seat and floor of the truck for quite some time. I have replaced the shocks a couple of years ago. I always thought that the vibration was from the tires. I recently replaced with BFG Long Trail TA Tours and had them road force balanced. The shocks have been replaced with Monroe Sensatrac shocks. I have replaced all the brake rotors and pads with Wagner Thermoquiets. I have had the driveshaft balanced at a driveline shop. My vibration is felt at about 36-42 mph and then returns a high speeds such as 55 and above. It is speed dependent, it is felt when coasting in neutral. The roatation rhythm seems to be with the speed of motion. I recently reindexed the driveshaft and the rear end. It seesm to have decreased yet is still there. What do I do next to repair this annoying situation?

Thanks,

John

ANSWER: hey there, i need to know one thing.does this truck have a hanger bearing on the drive shaft???  let me know
Chris P

---------- FOLLOW-UP ----------

QUESTION: No hanger bearing. It is a long single drive shaft.

John

Answer
hey there again, well there can be a few items that can cause a vibration. does the engine possibly have a misfire under lad?? but if this is a vibration when speed icreases, try having the drive shaft balanced, Local dealers will be able to tell you where to go to have this done, cause believe it or not the drive shift has to be balanced just like a tire would have to be balanced. If this doesnt solve your problem let me know, good luck
Chris P