Santander Consumer USA has inked a deal to acquire DriveTime Automotive Group’s $700 million portfolio of finance receivables, which includes installment sales contracts, certificates representing residual interests in securitizations, and “certain other assets,” according to a filing with the Securities and Exchange Commission dated Sept. 11.

The sale is part of a broader move by DriveTime to sell the Phoenix-based buy-here, pay-here company. Once the sale of the portfolio closes, a “new entity owned by third-party investors” will buy DriveTime’s 91 dealerships and 16 reconditioning facilities for an undisclosed amount, according to the filing.

Santander has been one of the most voracious buyers in the auto finance sector in recent years. Ranked No. 14 by the 2012 Big Wheels Data Report, Santander has largely grown by acquisition. It bought $3.2 billion of CitiFinancial Auto’s loan portfolio in 2010 and agreed to manage another $7.2 billion of Citi’s auto loans. In 2009, Santander bought HSBC Finance Corp.’s auto loan servicing business and $1 billion of receivables; it also bought lender Triad Financial. Santander also formed an alliance with Chrysler back in 2010 to provide subprime financing, subsidized by the carmaker, to consumers with subprime credit.

DriveTime, which has been steadily growing, operates in 18 states, primarily selling three-to-seven-year-old vehicles. Earlier this month, it picked a fourth location in Alabama, which is slated to open Nov. 16. DriveTime has more than 150 open positions, according to its website.

As a result of the sale, Standard & Poor’s has assigned a “CreditWatch with developing implications” designation to the ‘B’ ratings of DriveTime and its $200 million of senior notes.

“The CreditWatch reflects our view that there is a good likelihood the parties will complete the transaction, as well as our belief that there is not enough information available at this time about the eventual capital structure and ownership of the newly formed acquiring entity,” according to the S&P announcement.