Updated from 11:34 a.m. EDT Shares of Tenneco Automotive ( TEN) were among the NYSE's big winners Tuesday after the company reported better-than-expected second-quarter earnings and sales, and said it expects to perform well during the second half of the year. The Lake Forest, Ill.-based auto-parts maker reported pro forma earnings of 70 cents a share on sales of $1.11 billion. Analysts polled by Thomson First Call had expected it to earn 54 cents a share on sales of $1.05 billion. Looking ahead, the company said that it is "cautiously optimistic" that its improving performance will continue during the second half of the year, despite "market uncertainties." Shares of Tenneco Automotive traded up $1.88, or 15.2%, to $14.23. Radio Shack ( RSH) rose after the company exceeded second-quarter earnings expectations and raised third-quarter guidance. Second-quarter earnings of 42 cents a share easily beat the 39 cents analysts had expected. Sales, meanwhile, came in at $1.05 billion, in line with expectations. Looking ahead, Radio Shack expects to earn 38 cents to 40 cents a share during the third quarter. Analysts were expecting it to earn 37 cents a share. Shares of Radio Shack traded up $1.94, or 7.2%, to $29.02. Shares of Converium ( CHR) got ripped after the reinsurer warned that second-quarter earnings would fall short of expectations. The company said its results would be negatively affected by a reserve strengthening of $400 million in connection with casualty losses related to underwriting the years of 1997-2001. Shares of Converium traded down $11.12, or 44.4%, to $13.90. Ceridian ( CEN) fell after it postponed the release of its second-quarter earnings, which were due out today. "A concern was raised internally very recently regarding capitalization and expensing of certain costs in our U.S. Human Resource Solutions business," the company said. The company, which initiated the review, notified the Securities and Exchange Commission about the situation and is cooperating with the commission's request for additional information. Shares of Ceridian traded down $2.13, or 10.5%, to $18.21.