Chrysler, in a regulatory filing, said Fiat now owned 53.5 percent, on a fully diluted basis, of the carmaker, which returns to foreign ownership four years after its partnership with Daimler ended.
The union trust fund and Fiat, which has controlled Chryslers operations through a minority stake purchased in 2009, are the only remaining shareholders in Chrysler.
Fiat has said it expects to gain an additional 5 percent stake in Chrysler by issuing new shares by the end of this year, which would, in effect, reduce the size of the U.A.W's stake in Chrysler. Sergio Marchionne, the chief executive of both Fiat and Chrysler, last week said he planned to merge the management of the two companies, which would then operate essentially as one.