Upgrade 3G from iOS 3 to 4 and preserve baseband

[hydroponik]

I'm trying to help my friend out here and don't want to screw up her phone.

Basically I need to upgrade from 3.1.3 to 4.2.1, but I need to preserve the baseband so I can still use ultrasn0w to unlock.

Would these be the correct steps to do this:

1) Download 4.2.1 IPSW for 3G (I found this site http://www.felixbruns.de/iPod/firmware/)
2) Use sn0wbreeze to make a CFW
3) Enter DFU mode and restore with iTunes?

I just want to be sure before I proceed, don't want to brick and mess with the unlock, hope you experts can help.

 

[mmntech]

Unless you absolutely need to, I'd keep the 3G running iOS 3. It runs considerably better.

 

[dawks]

I'll second that a 3G runs BRUTALLY slow with 4.x. Borderline unusable.

 

[hydroponik]

Well I found a great tutorial on how to do this, and I was able to successfully upgrade, but you guys are right, it's pretty sluggish now...

The main thing was we wanted to be able to use apps since most only work with iOS4+, and to get rid of a battery drain issue which I assume was from jbme.com using hackivate instead of using an att sim.

 

[kelvin18574]

Why don't you just buy her a iPhone 4? It's only like $400 on the market

 

[alent1234]

she's probably on t-mo

 

[kelvin18574]

Factory unlocked to win her heart <3

 

[manly]

Well I found a great tutorial on how to do this, and I was able to successfully upgrade, but you guys are right, it's pretty sluggish now...

The main thing was we wanted to be able to use apps since most only work with iOS4+, and to get rid of a battery drain issue which I assume was from jbme.com using hackivate instead of using an att sim.

not sure if I'll bother but you can run a script (from the whited00r tweaked firmware) that could speed things up:
Re: iOS4 Custom Firmware for iPhone 3G iOS4 Based

source: Page 9: iOS4 Custom Firmware for iPhone 3G iOS4 Based