By Doron Levin

If the new General Motors truly is a different company, it can ratify that claim by shrewdly managing AmeriCredit, a Texas-based subprime lender it's buying for $3.5 billion. More broadly, GM has to learn once again how to profit from automotive finance while remembering that its main business is car-making.

The old GM's management of its GMAC lending subsidiary was dreadful. In the bad old days, GMAC financing became the tail that wagged the dog, providing incentivized leases, cash rebates and 0 percent financing as catnip to shoppers unimpressed with GM's vehicles. Old GM morphed into an automaker that sold deals, not cars.