1. Download the file below and rename it to “update.zip”
2. On your Vibrant, go to Settings > Applications > USB Settings > and select Mass Storage.
3. Connect your Vibrant to your computer, and mount as a mass storage device by pulling down the notification bar at the top of the screen.
4. Back on your computer, look for a new drive. We’re looking for the Internal Storage, not the External, so make sure you open the drive that does NOT have the Avatar movie in it.
5. Copy (drag and drop) the update.zip file to the Internal Storage.
6. Turn off the phone.
7. Hold down the volume up and down buttons while turning the Vibrant on, which will bring you to the recovery mode.
8. To navigate in Recovery, use volume up and down to move, and Power button to select. Select ‘Reinstall Packages“
9. After installed, your phone will reboot, and will have the Superuser app, as well as Busybox installed.
10. You’re Rooted!
http://www.intomobile.com/2010/07/20/root-your-samsung-vibrant-tutorial/