The effects of the Fed’s half-point rate cut in September and its quarter-point cut in November have largely been passed through to auto loans, which fell on average from a peak of 7.3% in July to 6.8% last month, said Ivan Drury, director of insights for Edmunds.com.

These are today's mortgage and refinance rates. Mortgage rates might not drop as much next year if the Fed only lowers rates a couple of times.

"If there are blanket higher tariffs on all goods crossing the border, then there will be higher inflation. If there are tariffs on a few select products, which are done in phases spread over many years, then there will be less upward pressure on inflation. It also depends on how much and how fast U.S. factory production can ramp up," Yun says.