After all my whingeing about the catastrophic effect iOS 4 has on the iPhone 3G’s performance, I’ve become quite adept at downgrading it: I tried 4.0 and downgraded, then 4.0.1, and had to downgrade that. There are a few how-tos out there but I felt that some were too complex and that there were a few issues that weren’t being raised. So here’s my take on it: how to downgrade your 3G from iOS 4.0 or 4.0.1 to OS 3.1.3.
We can’t stress this enough: the downgrade will wipe your iPhone, and once you’re back on OS 3.1.3 you can’t restore data from backups made in iOS 4.0 or 4.0.1. That means if something hasn’t been copied from your iPhone to your computer and you’ve added it since upgrading to 4.0 or 4.0.1, you’ll lose it permanently.