Hi Eva
I have a client in the truck repair business (they don't sell them though). They use PACCAR as their truck maintenance software, including billing. It is integrated with Adagio AP, AR and GL. It works nicely.
I wouldn't recommend Adagio in order to track maintenance. This is one of those cases where industry-specific software is a better fit.
If you want to write to or talk to my client, email me at steve@sschwartzcpa.com
Steve