I HAVE 04 CHEVY SILVERADO Z71 EXSTENDED CAB 5.3 4+4 .I HAVE A WHISTLING NOISE STARTS AROUND 1200 TO 1500 RPMS when accelerating and goes away when letting off.checked for air leaks none and changed TB gasket and cleaned no difference. put back wheels up and drove and no noise only does it when driving down road ,brought to shop and they have no idear ,can realy hear noise driving along a wall or fence sometimes it sounds like a bearing spinning and whistling never gets louder or faster ,can put truck in neutral at 70mph and rev motor and does not make noise.at witts end anyone can help would be greatly apprecated thanks

 

In case any one else had same problems i figured it out i changed the center support bearing and whistling noise is gone after countlss hours of trying to figure it out.I broke the old bearing apart and it had grease and looked ok i didnt think it was it but it was .