Pigwich wrote:That post helps. Found the culprit. It's the bolt on the lower part of the U-joint where the spline actually comes OUT of the floor. not where the U-joint connects to the long shaft that goes up the steering column.
The exact same thing happened to me. At around 9,500 miles, "something that sounds like it's under the dashboard" started horribly rattling on rough roads at slow speeds, and the steering developed a new sound and looseness of play when moved left and right a bit. My Bolt was built December 2016.
It appears the problem is that a loose lower shaft bolt allows the intermediate shaft to travel up and down on the spline bit when the spline bit bumps up and down. Although the bolt on mine felt tight even with a socket wrench (I don't have a torque wrench), I could move the intermediate shaft up and down a fraction of an inch with my bare hands.
I loosened the lower shaft bolt, pushed the intermediate shaft as hard as I could onto the spline (tapping it down a bit with a rubber mallet), and tightened the lower bolt again. I can no longer move the intermediate shaft up and down with my hand and the rattle seems gone.
Pigwich wrote:I just can't keep from going back to that scene in Fight Club on the airplane.
Yeah. Jeezums, Chevy. I guess this is my fault for buying one of the first few hundred Bolts, but WTF?
Thanks for posting the solution, Pigwich and others.