Theres a book in GT5 Collectors Edition which tells you about the circuits and drivetrains and suspensions etc if thats what you mean. I havent played GT4.
If they do, it should be online. I'll bet that PD is going to make many changes to GT5, so it's best to have an online version where they can frequently keep it up to date.
Hey!
Even if this request is 11 Years old... i DO know a good one. 228 PDF-Pages... full of useful knowledge... and lots of additional pictures as "explainer". The file is legally available at archive.ORG: