Do transfer case repair problems track days with ice across states?

Across U.S. states, NHTSA owner complaints about transfer case repair run higher where days with ice are higher, after adjusting for the makes sold in each state. This is an association across states, not proof that days with ice causes this repair.

How to read it: Each dot is a state. Further right means more days with ice; higher up means more complaints for this repair than expected (1.0 is average). If the dots climb to the right, reports of this repair rise with days with ice.

What it shows: States with more days with ice tend to sit higher on the chart across 22 states: a pattern in the data, not proof of cause.

• The 7 states with the most days with ice (Minnesota, Wisconsin, Michigan, New York, Illinois, Ohio, Indiana): reports of this repair run 57% above what the makes sold there would predict, and 6 of 7 are above expected. The 7 with the least (California, Florida, Georgia, South Carolina, Texas, North Carolina, Virginia): 26% below, and 1 of 7 are above expected.
• Exceptions: Indiana is among the highest in days with ice but reports below expected.
• Split the states into thirds: the third with the least days with ice runs 26% below what the makes sold there would predict, the middle third 19% above, and the third with the most 57% above. It steps up steadily.
• For days with ice, after allowing for the 1562 comparisons we ran, luck alone would produce a pattern this strong about 1 time in 10,000 or more. Take out any single state and the days with ice pattern still holds.
• Weak spot: compare only states with similar very hot days and the pattern keeps about 50% of its strength, so part of it may come from very hot days instead of days with ice.

Road salt and slush corrode exposed metal and seize moving parts, and freezing weather stiffens rubber, so repairs to exposed parts can follow harsh winters.

Source: NOAA U.S. Climate Normals 1991–2020, joined to NHTSA owner complaints · file downloaded 2026-10-06