If you are able to stop Postgres on the slave you are taking the base backup from, you could do this:
I'm not... the data base is 2 TB.
So, a RSYNC would take DAYS..... And I'm not able to stop the SLAVE for that long time
Depending on when you took the base backup and how many changes have occurred at your source (slave1) database cluster, the rsync execution time may or may not take as long as a new base backup if is only only shipping deltas (changed files).