iphone OS4 downgrade

[nairdie81]

hello fellow iphone peepz, i accidentally upgraded my 3G to the 4.0.2 software. I would like to know if theres a way i can downgrade to 4 or even 4.0.1. i cant unlock it anymore with 4.0.2. thank you in advance.

[eyeRobot]

Ultrasnow can unlock 4.0.2. Are you jailbroken?

[nairdie81]

no...i was trying to use the jailbreakme.com but it says d version is too new. how can i jailbreak a 4.0.2??

[eyeRobot]

Redsnow 0.9.5b5-5 can jailbreak, just double check that the unlock is supposed to work with it.....

[nairdie81]

i mean..i cant jailbreak it with the jailbreakme.com? is there any other way i can jailbreak a 4.0.2? thanks

or is there a way to downgrade from 4.0.2 to 4.0 or even 4.0.1??? thanks.

[eyeRobot]

Yes, as I said, you can use Redsnow to jailbreak. Here's a link:

Jailbreak iOS 4.0.2 with Redsn0w [How to Guide] | Redmond Pie

Then use ultrasn0w to unlock.

You could downgrade only if you have SHSH files saved. Use tiny umbrella to see what you've got!

You are right that Jailbreakme is no use to you on 4.0.2

[nairdie81]

westonben....thank you for your quick replies....and i will definitely try that link. im not so familiar with the "shsh files" nor the "tiny umbrella" although i have read those hear at the forum. nonetheless, thanks again for your help. i appreciate it. thank you.

[eyeRobot]

There are good write ups on SHSH files which explain it far better than I ever could, but basically, when you do a restore or upgrade in itunes it checks with apple that you are using only firmware which apple is currently signing.

Cydia (Saurik's server) is keeping everybodies SHSH files on store to circumvent the apple server, but you need to make sure you request those SHSH files to be saved there. One way to do this is when you first Jailbreak and open Cydia it asks if you want Cydia to store those files, clicking "make my life easy" will request the SHSH files from apple at opportune times, so even if you stayed on 3.1.2 cydia would request the 4.0.x files without you upgrading. Tiny Umbrella is a tool which you can use to check which files Cydia has on store and if it doesn't have it it will try to get it from apple and store it. You can use tiny umbrella to see which ones you've got.

If you have any (and if you were previously jailbroken then you've probably got some) then you can downgrade to that firmware. Check out the downgrading guides.