And a former Chrysler engineer agreed, in an interview with Automotive News, that the hitch would provide little protection in high-speed, high-energy crashes of the type identified in NHTSA's request.
"It's just not going to work. You have too much force applied to the material, and it's going to exceed the yield strength," said Bob Sheaves, a former Chrysler design engineer and now a Detroit-area engineering consultant.
Still, regulators say they're OK with Chrysler's plan. U.S. Transportation Secretary Ray LaHood told The Detroit News last week that he was "absolutely" satisfied with the modification. "It means that [owners] will be protected," he told the newspaper.
In a statement to Automotive News, NHTSA said: "NHTSA believes the risk of post-crash fire and fuel leak incidents it evaluated would be mitigated by the remedy now offered by Chrysler. However, the energy involved in some crashes is so extreme, and the structural damage so severe, that any passenger vehicle involved in such a high-energy crash may experience a fuel leak or fire as a result.
"The purpose of the remedy is to reduce the likelihood of damage to the fuel system that results in a fire or leak, and is likely to be most effective in lower- to medium-speed crashes."
Previously, the agency had cited graphic examples of high-energy crashes, and resulting fires, in its recall request.
The agency did not rule out further testing of the SUVs equipped with the trailer hitches.
As part of the agreement, Chrysler will install hitches on up to 1.56 million of the vehicles. But for 1999-04 Grand Cherokees, Chrysler will only replace any existing aftermarket trailer hitches if they have sharp edges.
Chrysler, which says the Jeeps met applicable safety standards at the time they were built and are not significantly different in design than competitors' models, hasn't identified the exact part it will use on the Jeeps.