Years ago there were strict rules about capitalization of smaller (less significant) words in a title. I believe that is changing, and I think it's a good idea [ after all, the prepositions and articles, although smaller words, could make a significant change in the meaning of the title if changes ]. Besides, I recently bought a book that had every word capitalized [ even 'a' in the middle ].
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vutdoan"Trouble on Wheels"This is a matter of style rather than grammar. Capitalising even short words like articles and prepositions is probably more common in American English than British English.
or
"Trouble On Wheels"