Tax implications on trailers less than six months old

Two months ago, my company purchased a new trailer from a dealer for use in our business. The sale of the trailer by the dealer to us was taxable under Internal Revenue Code Section 4051. Unfortunately, the trailer we bought is not sufficiently meeting our needs. One of our customers has indicated an interest in buying the 28,000-pound GVWR trailer for use in his business. A friend told me that if we sell the trailer within six months of its purchase, the sale would be subject to Section 4051 tax. I thought the six-month rule only applied to the installation of parts and accessories. Please clarify.