I had a violation of restricted license charge in 2005. I had to go to court. Since it was my first offense, the judge did an "Adjudication Withheld" and I only had to pay a fine. Will that deny me entry to Canada, even if I am just transferring planes in YUL? I have a US Passport.
Canada cares very much about drunk driving and will deny entry to anyone who has been convicted of it, even if it was not considered a serious offense in that person's home country. Canada may also refuse entry if you were convicted of what they call dangerous driving. Based on your description, that does not seem to be what you were convicted of.
If you are asked about your driving or criminal record, you will need to explain the situation. Typically you won't be asked, unless you are referred to secondary inspection for some other reason.
Canada has an extensive page explaining what crimes they consider to make someone inadmissible and how to overcome that inadmissibility.
One item in particular mentioned on that page is that you can contact the visa office in your country to find out if an offense for which you received a record suspension or discharge (in your case "adjudication withheld") would make you inadmissible to Canada.
If you received a record suspension or a discharge for your conviction in another country, check with the visa office that serves the country or region where you live. It will tell you if the pardon is valid in Canada.