Nice try!
It’s not whether there were Jewish translations, it whether what the Church now calls the Septuagint is the same as what Jews called the Septuagint before Jesus. It is manifestly not.
Exactly which Jews are you referring to? There were at least five different Jewish Canons that I am aware of; The Sadducee, the Pharisee, the Essene, the Septuagint and the Babylonian, none of whom agreed. The Church accepts the Septuagint because partly because it was accepted by the largest number of first century Jews.
Here is an informed Orthodox Christian discussion of the issue:
http://www.monachos.net/forum/showthread.php?6922-Jewish-claims-about-the-Septuagint-Pentateuch-only
The real problem is that there was not one “Judaism” before Jesus and at the time of His earthly ministry, but several streams of Judaism. The Septuagint (meaning the entire Greek Bible) was a Hellenistic Jewish book, not a Rabbinic Jewish book.
Rabbinic Judaism, as it emerged after 70 AD, refused to acknowledge the Septuagint because of Christian use of it as a book of prophecy. Hence the idea that the “real Septuagint” included only the Pentateuch.
However, to this day, we Orthodox Christians see even the Pentateuch, in its Septuagint version, as containing prophecies of Christ, and we use it that way in our liturgies.