Upgrading 3GS 3.0 Old Baseband to 4.0

[Willy Voet]

Hi,

I have a jailbroken/unlocked 3GS with OS 3.0 with baseband 04.26.08 and original ATT sim, and I'd like to upgrade to OS 4.0 without updating my baseband. From what I can tell based on the how-tos http://www.redmondpie.com/pwnagetool-4.0-jailbreak-ios-4-iphone-3g-3gs/ , I should use PwnageTool to make a custom .ipsw file.

My question is, which ipsw should I use in PwnageTool?

Also, is there any chance call quality will improve by upgrading the OS? If I risk losing my unlock and upgrading my baseband will that improve call quality?

Is it still possible to tether in OS 4.0?

Basically, are there any downsides to upgrading my OS to 4.0? I'd like to keep my baseband at 04.26.08 because I switch sim cards when I travel. But if the call quality improves with an updated baseband I would consider upgrading.

Thanks,
Willy

 

[TMar]

First is this new or old boot rom? Second, why not update the baseband? You will not lose your unlock because all current BB's are unlockable. You'll want the 4.0 ipsw for you phone and they can be found HERE.. You'll also want to know if you have your SHSH save for 4.0 to be able to restore to it in the first place.

Yes, teathering works in 4.0.

 

[Myzhi]

First is this new or old boot rom? Second, why not update the baseband? You will not lose your unlock because all current BB's are unlockable. You'll want the 4.0 ipsw for you phone and they can be found HERE.. You'll also want to know if you have your SHSH save for 4.0 to be able to restore to it in the first place.

Yes, teathering works in 4.0.

It's gotta be old bootrom since he's on 3.0. And, I would keep it on 4.26 baseband. For that baseband, it's a very stable hack unlock compare to the other ones with all sorts of possible issues.

To OP, just create custom 4.0 firmware & keep 4.26 baseband with pwnagetool. Use it restore / update with iTunes. Do you have your SHSH hashes save just in case something goes wrong? If NO, suggest you hold off on updating until 4.1 JB is out and you can save hash for that firmware.