Garage band 08 files in Garage band 11 - problem

Hello, I recently opened up a Garage Band file from Garage Band 08 in Garage Band 11 and the bass tracks sounded like actuall keyboard tones instead of the bass sound with which they were created originally in GB 08. I also noticed that the drums did not sound the same either. (both the bass and drum tracks are not "real" but created in GB) Do i need to apply effects back to the tracks or something. Are the two versions not entirely compatible. My buddy and I would like to trade tracks as we record our guitar tracks direct, each on our own versions of GB - he in GB 08 and I in GB 11 - but maintain the bass and drum tracks that were created in GB 08 all the while as we trade the file between each other. Please help. Thanks!! Oh, i'm running 10.6.8 he is running an earlier OS, if that helps.

C