- Backup your Gmail contacts. Go to your Gmail contacts page, click More actions and then select Export... to download a copy of your current contacts.
- If you update some contacts information on your phone after it failed to sync, you need to manually update the changes to your Gmail contacts online.
- Make sure you Gmail contacts have all updated contact information.
- Erase all contacts on your Android phone. Go to your phone Settings > Applications > Manage Application. Go to All tab and search for Contacts Storage. (Tips: you can search the list by pressing the search button on your phone.) Open Contacts Storage and click Clear data.
- Once it's done, you can wait for next update or go to Settings > Account & Sync and click Sync all to force immediate update.
Now, the contacts on your phone should be identical to the one on your Gmail.