subject: How to downgrade your iPhone 3G from iOS4 [print this page] If you're an iPhone 3G owner that has recently upgraded to the new iOS 4, and have realized that your device now functions extremely slow, even too slow for the new features to be worth having, then this tutorial on how to downgrade back to iOS 3.1.3 is for you.
The first thing you will need is the iOS 3.1.3 firmware, which you can find here (this will ONLY work for the iPhone 3G). The file is slightly over 200MB, so it will take a decent amount of time to download. The next tool you will need in order to perform this downgrade will be a useful little tool called RecBoot, which you can download here.
Once both the firmware and RecBoot are downloaded, launch iTunes. Once opened, you will put your iPhone into DFU (Device Firmware Update) mode. Here are step-by-step instructions on how to put your device into DFU mode.
1. Plug your USB cable into the charging port of the iPhone.
2. Press and Hold the power button AND home button at the same time.
3. After exactly 10 seconds, release the power button. Continue holding the home button until your iTunes displays a message telling you that it has detected an iPhone in recovery mode.
That's it. Now your iPhone is ready to to downgrade to iOS 3.1.3. Select your device in iTunes under the "Devices" sidebar on the left pane. Now, hold shift on your keyboard while clicking "Restore". A window will pop up prompting you to select the firmware you wish to use. Navigate to the 3.1.3 firmware we had just downloaded, select that and hit open. iTunes will begin to install the firmware.
Once iTunes is near finished with installing iOS 3.1.3, you will receive a iTunes error 1015, DO NOT PANIC. This is part of the downgrading process.
Now, the final step. The iPhone will boot back up with the "connect to iTunes" screen. Leave your device plugged into your computer and locate the RecBoot file that you had just downloaded. Open RecBoot.exe and a screen should pop up. Click "Exit Recovery Mode", RecBoot will now push your iPhone out of recovery mode, and it will boot up with iOS 3.1.3. You are done. This process should work just about the same on OS X.
If you have any questions, contact an iPhone repair company. They will be glad to assist you with any questions you have regarding this process.
Note: This will be a fresh install, so if you had a backup BEFORE you upgraded to iOS 4, then you will be able to backup by using that restore point. If not, you are unfortunately out of luck.
