Hmmm, it's a tough one to call. Your pages are working fine for you at the moment so I'd probably be hesitant to change anything, however...
Although you have re-written the content, they each contain a similar link structure (e.g. all pointing to the same application form) and contain the same Youtube video link for example, so I wouldn't put it past an algorithm update to pick up on this, notice the similarities and frown slightly on it.
I suppose the 'correct' way in google's eyes would be to create a single (or just a few), rich content page(s) that offer fresh relevant content on each and lists all the types of truck that you can provide finance for and focus your efforts onto this/these few pages. This would make the page(s) relevant and there would be no irrelevant or duplication issues - but this would be time consuming and more than likely negatively affect your keyword rankings in the short term at least.
If I were you I would be hesitant to change something that is currently proving effective in your particular keyword niches until you actually notice a ranking drop, but others may offer a different opinion. You may just want to enrich the content further on your existing pages and try and make them stand out as being necessary. Perhaps put a bit more information about dump trucks on the dump truck page and a recent piece of news about semi trucks on the semi truck financing page - this would then differentiate the pages from each other more.
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