Best answer by Mathis
Thanks for posting. This is not possible - sorry. Once you've used up all 180 minutes of upload space allowed for free accounts, tracks that exceed your quota are hidden and you cannot upload more.
In order for all of them to appear on your account, you can either upgrade to a Pro plan or delete some sounds to make space on your account for new uploads.
You can check out what tracks are hidden on your account here: https://soundcloud.com/you/tracks. To delete click to 'view hidden tracks' and hover your mouse over the track for the 'trash' icon to appear.
Please note: deleted tracks can not be restored. If you have any concerns about this, let us know.
Hope I was able to clear things up for you!