Reduce the size of .pack files.

We are trying to port a repository from enterprise git to Git hub. But the repository size is 4+Gb and the process is not working.
We analysed and found out that the size of the .pack files in our repository is huge and is around 4GB. After further analysis we could see that some of the large files can be removed from history. Is this a plausibe solution that we could take?
Is there a documentation on the steps to be followed?