U.S. same-dealer used Class 8 truck retail sales fell 13% in May compared to April, according to preliminary data from ACT Research.

The decline was steeper than historical seasonal trends would suggest, as ACT said in a news release that typical seasonality would have pointed to a 3% month over month decrease.

While retail sales weakened, auction sales surged 79% month over month, while wholesale transactions declined 19%. However, year to date retail sales were down just 0.7%, and total used truck sales across all channels increased 2.9% compared to the same period last year. This is according to Steve Tam, vice president at ACT Research.

“Total reported preliminary sales finished May up 9.4% month over month. The fact that the total market is in sync with seasonal expectations is a welcome testament to the long-awaited balance and stability of the current market,” he said in a news release.

“The preliminary average retail price (same dealer sales) of used Class 8 trucks was steady in May, slipping a narrow 0.6% month over month to land at $59,601. Pricing easily defeated seasonal expectations, which called for more than a 5% decline,” Tam added.