Over the course of this year, my dually has developed a shake in the steering wheel when driving between 35 to 45 MPH, regardless if the truck is empty or loaded and the problem is more noticable during turns than straight ahead and it is a intermintent problem that on occasion does not occur however, it happens more often than not.

I have replaced the steering gear box, I have had all 7 rims and tires checked for true and balance and have tried rotating tires, and yet the problem persists. approximately 4 years ago it was aligned and the tie rods replaced, any ideas what else could cause this shake? thanks...