I drove the truck for its first long haul (400miles) and never relized how annoying the shake is, is it the tire balance, or is it an exhaust harmonic or what? It seems worse now than ever. Any comments?

 

wow, i thought that was only my truck. it is sooooo annoying though.

 

Do a search there were numerous discussions about this vibration problem. Unfortunately, there wasn't a firm solution to it but here are a few ideas that were discussed.

1. Exhaust vibrations. Solution was to loosen all of the exhaust fasteners and retighten. Some people added an exhaust dampner kit which was a Ford factory part. Basically clamps onto the exhaust tubing and controls harmonics. Some people changed the muffler and never had a vibration again.
2. Driveshaft could be bent, came from the factory with alot of runout, or wasn't balanced properly. Earlier L owners upgraded to the aluminum unit but still had vibrations.
3. Pinion angle. This is common with lowered vehicles but could still be a problem on a stock truck. Shims may need to be installed in bewteen the axle and leaf spring to correct the angle.
4. Some owners had the transmision tailshaft bushing "walk" out of it's bore which causes the slip yoke to vibrate due to the decreased support.
5. Bent or improperly balanced wheel.
6. Defective tires.

These were the most common discussions back then and might prove useful when trying to dignose your problem.........

 

I have been all over this one extensively. My findings have been improperer tire runout(out of round)improper balance,The biggest problem so far is the tonneau cover,when the wind blows over the ribs it give an shake in the seat,that can drive you insane.
Remove the tonneau and drive it I garantee it cuts down a lot of your vibration.Also you can go to a tire shop w/ a balancing machine that places load simulation on the tires and measures tire/wheel runout,to find out the condition of your rims and tires.Hope this helps Brian

 

Hmmm, don't have it..

 

The only cure I found was to sell mine. Seriously, I was never able to get it solved. Tried everything, and I mean all of the above mentioned suggestions. Tires, rims, driveshaft, exhaust. The only thing I was willing to try but never got to was to replace the aluminum driveshaft with a steel one. My vibration was temperature dependant and I felt the aluminum could be changing shape.

Good luck!!