Assuming that our patriarchs Abraham Isaac and Jacob spent time learning in the House of Study of Sheim v'Eiver, the descendents of Noach, what were they learning? The seven commandments of the Noachide Covenant are derived by Chazal (in tractate sanhedrin?) from pesukim in the Torah, but the Torah was not given yet. Assuming that the Avot were shomer torah u'mitzvot before matan torah, how could they learn torah and understand ratzon Hashem (noachide covenant or sinaitic covenant) if they had no access to study the Torah because it was not given yet?
I asked my Rav this question once. He answered that they would learn theology such as belief in God and the mitzvot Ben Adam Lechavero that are obvious (such as גזל). I guess it would be best comparable to ibn Pequda's Chovot HalLevavot, parts of which he derives from what he calls "sekhel". He also pointed out that they must have had some form of mesorah in certain halachot, for example Noach knew to differentiate between Behemot Tehorot and She'eynan Tehorot, and this institution kept this mesorah alive.
Emes LeYaakov by Rav Yaakov Kamenetsky Genesis 28:11 answers this.
In brief summation Rav Kamenetsky suggests that the Torah learned in the Yeshiva of Shem and Ever is the "Torah of Galut" (exile). And Yaakov needed to learn it before he went to live with Lavan so that he could deal with the hardships over there. It also explains why he taught it specifically to Yosef, and not the other brothers, as Yosef was the one who had to go down to Egypt and represents the prototypal Jew in Exile
I heard once in a recording of Rabbi Tatz (which was based off of Rav Moshe Shapiro's teachings - as reported from @AKayser) that in the Yeshiva of Shem and Ever they learned spirituality that was disconnected from the physical. Therefore, Rivka, when she had (what she thought was) one child with an urge towards avoda zarah and the beis medrash (meaning he had a disconnect between a spiritual drive and physical pulls), she went to seek out the counsel of Shem and Ever. When Yaakov was going to the house of Lavan, where it was necessary to know the Torah of the disconnect between the physical and spiritual, as Lavan had a lofty soul (he shared a Neshama with Bilaam, who received prophecy on the level of Moshe) and yet lived a life of trickery, he stopped at the Yeshiva of Shem and Ever for 14 years - after having grown up in the house of Avraham - to learn the Torah that was necessary for dealing with such an environment.
Avraham on the other hand taught the Torah which was meant to influence every facet of the physical.
For this reason, Nimrod saw Avraham as a threat and had him thrown into a fire, while Shem and Ever were at large teaching Torah and Nimrod wasn't bothered - their Torah didn't tell you how to live your life.
(Much more left out, I'm sure you could find the recording at www.simpletoremember.com)