OK this may all sound stupid but a buddy with a 98 Dak had this problem. It turned out that the original owner turned it in with this problem from the factory. The truck it self was a total misalignment with the frame and suspension. No one ever new until it was taken to a frame suspension specialist up in Camden NJ who found the problem after some twisting and pulling the total aliment was achieved and the truck rode total normal at all speeds. My buddy did all the things you did tires shocks ball joints etc and nothing helped and for good reason. Why my buddy didn’t find this problem during his test drive? He never got the truck over 45 mph and drove it on a smooth surface according to him. Hope this may help.

 

I could be off here (like most of our assumptions) but I just had something very similar with my 06 dakota QC 4.7HO. speeds from 55-65 I had a hard vibration in the truck. this actually started after getting my wheels and tires balanced. it wouldn't always happen and i could only duplicate the problem about 75% of the time.

turns out the retards who balanced my tires did not know how to use the machine properly. if you have rims w/ the chrome cladding on them, they cannot use the metal cone on the machine from the outside of the wheel. they must do it from the inside. all of my tires were about 3oz off once I figured out this problem! got them rebalanced the correct way and problem is solved. although this sounds as if your problem could be different!

here are some suggestions I got from another forum before registering on here...

wheel balance (no tires on the wheels ... have them clean the wheels while the tires are off)

wheel runout (no tires on the wheels)

wheel and tire balance

driveshaft balance (you should be able to tell if a weight is missing)

alignment (incorrect toe / caster can cause odd vibrations at certain speeds)

rotors / brake pads / wheel hubs

tie rod ends for play, idler arms for play, sector shaft for play at the bearing.

shocks for blown gaskets and low oil (if they are leaking ... replace them)

steering stabilizer for blown gaskets or leaking oil (not sure if you have one)

all your steering mounts, motor mounts, control arm mounts (A-arms), and any bushings (front AND rear ... you would be surprised what rear anomalies will cause vibrations in the steering wheel)

 

I forgot about the chrome clad wheel problem with balancing. I had that issue too.
Nice post.

 

After the hard time the dealer gave me to replace the struts I bought my own," Monroe"! No way I was going to use factory spec'd struts. But my problem has been isolated to the front. The forensic mechanic put it on a dyna pack, The dyno bolts to the hubs with out the wheels, and the rear was solid, so they can't say the wheels are at fault. And they did change both lft and rht side cv axles, drive shaft and U joints.

 

Wow. Sorry that you have to go through all of this. Although, I can't wait to hear what the fix is. You'll get it eventually. Can you remove the front axles and drive around? If you've isolated it to the front, maybe you can isolate it to the front wheels/hubs/brakes/steering rack etc that way. I'm starting to think rack. Haven't some others had rack problems? Inner joints?

 

Did you ever find a fix?

 

i have a slighty shimmy when i hit 142 mph on the highway but thats just the truck say not so fast, other than that my truck is still solid with 85000 miles on it. i wouls check the driveshaft to see the weight fell off, or even the rear brakes

 

Still waiting on that video...