05 Silverado trans issues

when the trans shifts,I feel a slight shudder.sometimes when passing I get a clunk from beneath.I have lubed the slip yoke and checked the u joints.Also checked rear diff backlash.The dealer told me that the convertor dont lock untill 3rd so I ruled it out as well.It's at lower speeds that I feel it most.Could it be u joints despite them feeling tight and snug still?Fluid looks good...it has 50k on it now.It is a crew cab/short bed.I just purchased it.

The reductions, to begin in September, will occur in the Atlantic and Pacific regions, where Delta has experienced the greatest softness in sales, according to a letter to employees from CEO Richard Anderson. Trans-Atlantic capacity this winter will decline by 11 percent to 13 percent over the year-ago figures, while trans-Pacific traffic is down 12 percent to 14 percent.