Weird vibration at freeway speeds

So, I have been having this weird vibration at freeway speeds and figured I'd ask you guys about it seeing as this is the second 1st gen truck I've owned doing the exact same thing... Ok so the vibration is in the front end obviously .. Can only feel it between 65-75 mph. It comes and goes. It will be shaking and I go around a curve on the interstate and it will go away completely and ride smooth as silk, then come back in if I change lanes or go around another curve. I've not spent any time trying to figure this out on this truck because I nearly drove myself insane with my last truck. It seems like the front wheels/axle assemblies will maybe move opposite as the front wheels rotate at different speeds while turning and either vibrate at the same pace, or cancel the other out for a smooth ride. Anyway, just figured I'd ask if anyone else has faught this problem.

About the two trucks old truck was an 02 3.4 5speed 4x4 ext cab.
Current truck is an 04 3.4 auto 4x4 dcab.

2.5 in lift on both trucks.
Bfg all terrains on both.

Did not do the diff drop on either truck and was gonna actually try that first on this truck.
02 truck had the wheels balanced on several different balances with the same result....none! Even road forced balanced and no change...

Both trucks ride smooth at 55 mph...

Ideas?

 

My guess would be tie rod ends on the front. Lift the front and see if you can find any movement.

 

Everything is tight. Both trucks have been aligned. No abnormal tire wear whatsoever

 

It may just come down to harmonics

 

Does anyone else's truck do this?

 

I'll put this out there..front diff bearing?

 

Chock the front wheels, put the tranny in neutral and get the rearend up in the air. Get a dial indicator and a magnetic base and check the runout of the drive(propeller) shaft. I have witnessed it many times where someone has replaced the ujoints and didn't mark the original position of the shaft on the rear flange prior to taking it off. It is critically important to put the drive shaft EXACTLY back on the way it came off or you get a vibration as you describe.

 

Does it go away in 4hi? If zo there is a fix for that! Ive always owned older tacos than the 01-04's so ive never had to deal with this first hand but ive read about it several times. ECGS sells a tool and bushing to fix the issue. Hopefully someone with experience on this will chime in!!

 

The bushing you're talking about doesn't exist on my truck. Arb front and rear diffs. with new axles up front and they are tight as a tick...

 

So puttin a locker in the front does away with that bushing? Again no in person experience with this but I thought it was in the jackshaft...idk..

 

The bushing supports the weight of the half shaft. Arb has the bushing already installed into the diff. Non existing may have not been the proper wording...