Jvalops,

This is a common scenario in SEO when you have 2 versions indexed of the same URL. This bascially creates a duplicate issue. Now, this situation has a solution which includes 2 things to implement:

1. Fix it from the search engines's perspective.

2. Make changes at the server level.

You did remove the trailing slash so you fixed it at the server level but you left the search engines to think - Where did the URL go? Am I supposed to show a 404 for that or what?.

So, it is important that you first fix them for the SE's and then make any server level changes because you never know how quick the crawlers can re-visit the disappeared URL and take their own action. Since this is just a recent change I hope that the SE;s will not evaluate it in a negative way but you should be quick to inform them. Now, since you have already removed it, do add a code in the .htaccess file stating that any URL with a slash redirects it to the URL without slash. I hope there are no URLs that have to end with a slash (just have a re-look on this, the home page and others).

After this is done, to make things more clear to the search engines, resubmit your XML sitemap with all the correct URLs on the website and I think you will be just fine.

On the rankings, I don't think it will be affected, unless there was a re-crawl after the indexation.

Cheers,