Just curious - why would you have a secondary replica that is not configured the same as the primary replica? If you failover to that secondary and it isn't the same then you are almost certainly going to encounter issues.
And if the drives on the primary are extended past the point where the drives on the secondary can be extended - once your data and/or log file exceeds that size on the primary then you end up impacting the primary because the secondary is waiting to extend the files.
I would have a new volume created and presented that matched the size of the volume presented to the primary. I would then shut down SQL Server on the secondary and copy/move the files from the original drive to the new drive. Relabel the old drive to an unused drive letter - relabel the new to the old drive letter.
Note: to copy/move use something like Robocopy with the parameter(s) to copy permissions. If not - then you have to manually set the permissions on every folder which can be a pain.
Another option: have your SAN team do the work on the SAN itself. At a set point in time - shut down SQL Server - have the storage team finish replication and swap in the new volume for the old volume. Set permissions and restart SQL Server...