Has anybody had this problem when going over small bumps or pavement ridges on the driver's side? To me it sounds like a loose bolt underneath the dash up by the steering column. Dealer tried to fix it once and they lubed the steering shaft in accordance with a TSB that is out on the Silverados. The lube solution is GM's new fix revising a previous TSB which called for replacement of the intermediate steering shaft. Anybody else having any problems? The lube job on my steering shaft did not cure the problem. 
