Need Help Diagnosing problem, Please HELP, Very important.

Truck, 05, dually, 4door, 6spd, 80K.
Trouble, Horrible vibration at various speeds and it seems to be set off by bumps in the road. When it happens, you have to decellerate to about 20mph to get it to stop. It feels like the front end is bouncing up and down very rapidly.
What I've done, front shocks (rears out of stock at time of purchase) steering stabilizer, track bar bushings.
I assumed track bar bushings right off the bat because of all the troubles in years past but at 80K they actually didn't seem bad.

At first it was every once in a while on a really bad section of freeway at 75mph. Now it is happening A LOT and at various speeds.

I have checked ball joint and wheel bearing play, yes they need to be replaced soon but there is only a very little play in them.

My wife is on her way to California with a load of 10 horses and she almost lost control of the truck last night in BFE wyoming because of the vibration.

Please help if you have any suggestions, she is scared ****tless to go over 55 now.

Thanks in Advance.

 

I read this problem is generally caused by one or combination of three things:
1) Bad steering damper
2) Tire out of balance
3) Loose bolts on steering box mount

Good luck.

 

yea what he said........ if none of them fix it i would look at your tierod ends make sure they are ok.. then move on to checking you caster adjustment...what you are experencing is knowen as "death wobble" i had the same problem after i put the leveling kit on my truck i reset the caster and problem solved...

 

if you still have a shake check alignment too much caster will cause (death wobble ) that is if everything is tight in suspesion. Does the truck have a leveling kit ? if so take it off.
good luck

 

Shakes

Ya might check the U-Joints. They can cause some funny shakes and noise. Then when ya slide under the truck to look em over, they look OK. I had to torch a couple loose on my 03. Good luck in finding the problem!!