Upgrading and Unlocking 4.0 on iPhone 3gs 3.1 non jailbroken

[Money Over]

Hey,
I just want to double check that I am doing this right. I have an iPhone 3gs on 3.1 and what to update to 4.0 but unlock and jailbreak. Do I need to jailbreak my iPhone 3gs on 3.1 first and then update to a custom 4.0 firmware or can I just restore to 4.0 custom firmware? Thanks

[Simtech]

Yes.

[Money Over]

Which one lol update to 4.0 custom from 3.1 or jailbreak 3.1 first then update to 4.0 custom?

[destro23]

JAILBREAK FIRST! this way cydia can store your shsh blobs(so you can downgrade if need be)

[Money Over]

Right so I try and restore to a custom firmware and iTunes give me an error 1600?

Okay so I think I need to update my iPhone 3gs to 3.1.2 so I can unlock. However I try to do this and I get an error from iTunes saying that it cannot be update to the requested build? Im on a mac and iTunes 9.2? Thanks

[destro23]

iPod, iPhone and iPad Firmware Download

download the proper firmware and make sure you have a legit sim on hand. If you don't have shsh blobs saved for those other firmwares.. then i think you may be out of luck as apple has stopped approving other OS's

What did you jailbreak with? If you end up jailbreaking with spirit you can follow the tutorial below..

IOS 4 jaibreak for Spirit users with old bootroom

[Money Over]

I havent jailbroken yet. I now want to jailbreak but im on 3.1 and cannot update to 3.1.2 to unlock because I do not have the shsh files

[Go Gators]

If your on 3.1 firmware then you need to download the 3.1 firmware bundle not the 3.1.2. Then use redsn0w to jailbreak. After jailbreak launch cydia and save your shsh blobs then you can download the 4.0 firmware bundle and use use Pwnage Tool 4.0.1 to upgrade and jailbreak to ios 4.

[Money Over]

What redsn0w version do I need for firmware 3.1?

[zimpah]

Should be able to use any redsnow version. But Go Gators is absolutely right about the process you should follow. Don't update to 3.1.2. Could cause you some real hassles!