Finally long wait of iPhone OS 3.1.3 & iOS 4.0 jailbreak & unlock is over as iPhone Dev team has released both Ultrasn0w 0.93 unlock tool & Redsn0w 0.9.5 Beta 5 jailbreak tool for iOS 4.0. Fortunately the tools were released immediately after iOS 4.0 went live.
Please note: Redsn0w 0.9.5 Beta 5 is still in beta mode so you’ll need to let Cydia reorganize, reload, and update after using redsn0w.
How to Jailbreak iPhone 3G 4.0 with Redsn0w 0.9.5 Beta 5
4. Now follow our guide to manually update iOS 4.0 on iPhone 3G
5. Once you have updated iPhone 3G to iOS 4.0 start Redsn0w 0.9.5 Beta 5.
6. Click on Browse button and select iPhone 3G 4.0 firmware (iPhone1,2_4.0_8A293_Restore.ipsw) downloaded in step 1
7. Now click next and Redsn0w 0.9.5 Beta 5 will prepare data for jailbreak.
8. Now select “Install Cydia” and click Next. (If you want to disable multitasking & wallpaper then simple uncheck respective options).
9. Now You will need to power off your iPhone 3G and connected to computer only then click on next button of Redsn0w 0.9.5 Beta 5.
10. At this stage you will need to put your iPhone in DFU mode, to do this hold “Power” button and then while holding the “Power” button, you will now have to hold “Home” button too for about 10 seconds. Now after few seconds release “Power” button but keep holding “Home” button until installation begins (about 30 seconds).
11. Now just wait until Redsn0w completes the rest of the process. Once done, your iPhone 3G will restart automatically and you will find it jailbroken with iPhone firmware version 4.0.
12. If you want to unlock iPhone 3G 4.0 then follow our guide on How to Unlock iOS 4.0.
iPhone 3GS users can now jailbreak iOS 4.0 on iPhone 3GS with Pwnagetool 4.0.1 & jailbreak iPhone 3GS 4.0 with Sn0wbreeze 1.7 on Windows only if you have old bootrom, here is how to check iPhone 3GS bootrom, new bootrom users can check out how to jailbreak iPhone 3GS 4.0 New bootrom.