Downgrade iPhone 4 iOS 5 Baseband 4.11.08 to 4.10.01 to Unlock with Gevey Turbo SIM

UPDATE #6: If you own an AT&T iPhone, unlock it permanently using this.

UPDATE #5, 13 February 2012, 1.19PM (+7 GMT): To those who are interested on an alternative unlocking method, see here.

UPDATE #4, 25 October 2011, 11.38AM (+8 GMT): Hardware hack for you to consider.

UPDATE #3, 18 October 2011, 7.18PM (+8 GMT): One reader just commented that he was able to do downgrade, but I’m not sure if he did it much earlier. It’s still worth trying, though. I responded to his comment and waiting for confirmation.

I’ll continue to explore other options for everyone. Remember to subscribe or LIKE us on Facebook!

UPDATE #2, 18 October 2011, 11.06AM (+8 GMT): Sorry guys, Apple is no longer signing iOS 4.3.5. This tutorial is no longer valid. To those who managed to downgrade your baseband, good on you and remember to always preserve your baseband.

UPDATE #1, 18 October 2011, 11.00AM (+8 GMT): It seems like Apple had stopped signing iOS 4.3.5 for iPhone 4, I’m testing it now.

Did you blindly update to iOS 5 without realizing the consequences that it will also update your baseband to 4.11.08 that can’t be unlocked with your Turbo SIM? Thankfully, there’s still a way out, at least for now! Hurry before it’s too late! Apple had stopped signing iOS 4.3.5 on October 17, 2011.

Apple is still signing iOS 4.3.5, which means you can still downgrade to this iOS version. It has baseband 4.10.01 that can be unlocked with Gevey Blue Turbo SIM.

Here are the steps:

1. Download and install iTunes 10.4 or earlier. You will need to remove iTunes 10.5 first.

2. Download iOS 4.3.5 IPSW for iPhone 4 from Apple.

3. Put your device into DFU mode (search a tutorial on YouTube).

4. Connect to iTunes and it will say that your device is in recovery mode and needs to be restored.

5. Go ahead and click shift+restore (Windows) or option+restore (Mac). Select the IPSW you just downloaded.

6. iTunes will verify with Apple server and begins restoring your device. Once completed you will need the official SIM card to activate it. You can use other tools such as TinyUmbrella to confirm that you now have baseband 4.10.01.

7. Now download custom iOS 5 from here. Reinstall iTunes 10.5 in the meantime.

8. Download latest redsn0w from the Dev Team’s website or from here. Start redsn0w, go to Extras > Pwned DFU. This allows your iPhone to accept custom firmware. If you don’t do this, you will get error 1604, 1600 etc.

9. Connect your iPhone to your computer.

10. Click shift+restore (Windows) or option+restore (Mac) and select the custom iOS 5 IPSW you just downloaded.

This time your baseband will be preserved while running on iOS 5 and you can unlock it with Gevey Blue Turbo SIM.

Again – do it now because once Apple stops signing iOS 4.3.5, you will be stuck forever!

Did it work? Leave your feedback below.

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