Owners of the ASUS Transformer Pad Infinity generally seem to be pretty happy with the recent Jelly Bean update, but whenever there’s a big upgrade like that, there always seem to be users who want to downgrade. Whether you’re ticked that your alarm clock doesn’t work anymore, or you found that Chrome for Android actually performed better on the older firmware, I’m sure you have your reasons.

Luckily, in this case, it seems pretty easy to do, but it does require unlocking your bootloader and thus voiding your warranty. It also requires a bit of familiarity with ADB and fastboot.

If you’re OK with that, read on.

  1. Download the full, official 9.4.5.30 update from ASUS website.
  2. Unzip the file that you just downloaded from ASUS, and then extract the blob file that’s inside the second zip.
  3. Put the blob file in your ADB directory on your PC.
  4. Reboot the Infinity to the bootloader by turning the tablet off, and then holding down the power and volume down key. Select fastboot mode.
  5. In ADB on your computer, type this command: fastboot -i 0x0b05 flash system blob 
  6. Wait (be patient).
  7. The install will hang on the spinning ASUS diagram – this is normal! Once it does that, reboot into the bootloader and select “wipe data.”
  8. Your tablet will reboot, and you will have successfully downgraded from Jelly Bean to Ice Cream Sandwich.

Unfortunately, this doesn’t work for downgrading to previous versions of Ice Cream Sandwich, as you’ll get a signature error. But it works perfectly for getting rid of Jelly Bean.

[xda-developers]