Samsung rolled out the official Android 4.0.4 Ice Cream Sandwich upgrade for the T-Mobile Samsung Galaxy S3 SGH-T999 via the UVALH2 firmware update recently, but it seems that more goodies are in store for the handset as an official software upgrade, bearing Android 4.1.1 Jelly Bean, has leaked recently.

Build UVDLI3, the version number of the leaked software, can be applied to the phone through stock recovery. You can test out the leaked version for yourself right now.

The software also reportedly includes a new feature called Blocking Mode, which lets you disable some phone features at whim (e.g., incoming calls, notifications, alarm and timer, and LED indicator).

Take note though this is not yet the final official release, so it may still have some bugs and issues, although users have reported very little problems with the update.

This guide shows you how to upgrade the Galaxy S3 T999 to Android 4.1.1 Jelly Bean build UVDLI3 (leaked official update).

Warning

• The instructions in this guide are intended for use with the T-Mobile Samsung Galaxy S3, model number SGH-T999. Applying these instructions on another device or model may produce undesired outcomes.
• The information in this guide is provided for instructional and educational purposes only. There is no guarantee that these instructions will work under your specific and unique circumstances.
• Use these instructions at your own risk. We shall not hold any responsibility or liability for whatever happens to you or your device arising from your use of the info in this guide.
• Read and understand the whole guide first before actually performing the instructions.

Requirements

• T-Mobile Galaxy S3 SGH-T999 running stock, official Android 4.0.4 Ice Cream Sandwich software version UVALH2.
  • See our guide on how to upgrade the Galaxy S3 T999 to Android 4.0.4 ICS build UVALH2.
• Leaked Jelly Bean build UVDLI3 update file for T-Mobile Galaxy S3 (SGH-T999_T999UVDLI3-OTA-T999UVALH2_TMB_332312338.zip, 316.9 MB)
• Make sure your device's battery still has at least 70% power. You don't want the device to shut down in the middle of the procedure.
• Backup all personal data on your phone to make sure you have a copy of your personal data (e.g., contacts, SMS, MMS, Internet settings, Wi-Fi passwords, and the like) in case the procedure in this guide erases such data.
  • For backup tips, check our guides on how to sync your data to the cloud and how to create local backups of your mobile data.

Instructions

1. Copy the leaked Jelly Bean update file to the internal storage on your phone.
2. Turn off the phone.
3. Boot into stock recovery. To do so, hold down Volume Up, Home, and Power buttons together until the screen turns on, then let them go. In recovery, use the Volume buttons to scroll up/down and the Home button to select an option.
4. Select Apply update from SD card (or Apply update from internal storage), then scroll to and select the UVDLI3 update's ZIP file.
5. The phone is expected to reboot itself after installation. If it doesn't, return to the main recovery menu and select Reboot system now.

Fantastic! That should have done the trick and your Samsung Galaxy S3 SGH-T999 should now be running
Android 4.1.1 Jelly Bean build UVDLI3.  How does Jelly Bean feel like on your phone?