Fiat, owner of Chrysler Group, has agreed to buy the United Auto Workers' remaining 41.46% stake in Chrysler for $3.65 billion, plus four separate payments totaling $700 million.

The agreement, announced Wednesday, heads off a public stock offering of Chrysler shares that Fiat and Chrysler didn't want, but the UAW was forcing, in order to set a value on its stake.

It puts to an end months of cantankerous wrangling between the union and automakers about the value of the retirement trust's shares. And it's happened suddenly, in an unexpected way, as firm plans had been announced late last year for the IPO.

Fiat previously bought out the stake held by Canadian governments, so once the current deal closes, Fiat and Chrysler can be merged into a single company. No details have been hinted about where a merged automaker would have headquarters, nor whether a full merger would change product plans or management teams.