iPhone 3G (3.1.2 w/ 05.11.07) to iOS 4.x? (confused)

[tiritea]

I have an iPhone 3G that has already been jailbroken and unlocked (last year) still running 3.1.2 (7D11) firmware with 05.11.07 baseband, which I now want to upgrade to a 4.x OS in order to run some apps that requires the new OS version. However, everything I've been able to read on the web says dont upgrade to the current 4.1 OS if you want to keep the phone unlocked (which I need to because I travel overseas and use foreign SIM cards), and iTunes only lets me now install 4.1, not the 4.0.1 firmware version which best I can tell is the version I should go to.

There's lots of stuff on the web telling folks how to *downgrade* from an 4.1/4.2 firmware upgrade back to 4.0.1, but I've been unable to find any clear directions on what I should do in my position: namely *upgrade* from 3.1.2 to 4.0.1 and still keep an unlockable baseband.

Any pointers? thnx

- G

[iYeow]

Do you have a mac or pc

If you have a Mac, restore to custom firmware using Pwnage tools 4.1.2
If you have a PC, Download Ireb 4.1 and download Snowbreeze 2.0.2 from here : iH8sn0w.com | Jailbreak your iPod touches and iPhones
You have to download the 3g 4.1 ipsw from here to build your Snowbreeze firmware : iClarified - iPhone - Where To Download iPhone Firmware Files From
Run Snowbreeze in Expert mode, uncheck "activate my iphone " under general
Build it and it will be placed on your desktop.
Make sure you have updated your itunes first.
Run ireb 4.1 to put you into DFU mode
Itunes will ask you to restore
Do the shift + Restore to the Snowbreeze_4.1.ipsw
Make sure you leave your official sim in the iphone so it can activate after the restore
Now you are jailbroken at 4.1
Install Ultrasn0w from Cydia.

[tiritea]

Thnx for the quick response.

I have Mac (well, actually both if doing this is better via Windoze...). Yes, I saw several places indicating doing something with 4.1, but was pretty leery about it given all the warnings about 4.1 in general...

I'm running iTunes 10.0.1 (22).

So, basiaclly, I'll be downloading a new (?) 4.1 firmware, disabling its baseband update, and then 'restoring' up-level from my current 3.1.2 to 4.1?

BTW, I have Cydia installed already. Do I need to do anything about first saving my SHSH that I keep reading about?

[iYeow]

You do not restore to stock 4.1 , you restore only to custom firmware created by Pwnage tools 4.1.2. After you have created the CFW, you will be asked to put your iphone into DFU mode, just follow the instructions closely and you should be able to restore successfully to a jailbroken 4.1 and install Ultrasn0w from Cydia to unlock.

[eyeRobot]

You should, as good practice, download tinyumbrella and save your SHSH files too.