How to upgrade and Jailbreak iOS 4.0 from 3Gs 3.1.3 ??

[asdf212]

I have an iPhone 3gs 3.1.3 which I would like to upgrade to iOS 4.0 however, I would like to either keep or re-jailbreak the phone. Is this possible yet??

Thanks

 

[Applejuiced]

Early bootrom or new one?

 

[ACardAttack]

If you have old bootroom you can, there is a thread talking about it, if you have new boot room you cant.

 

[asdf212]

I think it is the old one.. How would I go about doing this if I wanted to try? Would I just use Spirit?

 

[Applejuiced]

I think it is the old one.. How would I go about doing this if I wanted to try? Would I just use Spirit?

If its old bootrom you can use spirit to JB it on 3.1.3
Then install spirit2pwn from cydia from the repo http://repo.woowiz.net. Then you can restore to custom 4.0 IPSW created with pwnage.
And there you have it a JB 3GS or 4.0

 

[Applejuiced]

And to find out for sure what bootrom version you have try this below.
How to Check the Bootrom Version of Your iPhone (Mac)
http://www.iclarified.com/entry/index.php?enid=10300

How to Check the Bootrom Version of Your iPhone (Windows)
http://www.iclarified.com/entry/index.php?enid=10301