After working on my Cricket/Aio Galaxy S4 for days and finding very little development tips, I decided to write my own full guide on how to root, install a custom recovery (TWRP) and flash a custom ROM for the SGH-I337z.
Before we begin, I am not responsible for any damage, including physical damage due to frustration, that you may inflict on your device. If at the end of this, your phone is nothing but an expensive paperweight, I must apologize, but assume no responsibility. If you are not comfortable using Odin or flashing ROMs, I suggest reading a little more on the subject before moving forward. This is a detailed guide for a specific device that is difficult to find help for. This isn't a step by step guide for a first time flasher. You have been warned.
First, download and install the Kingroot apk. Do a quick Google search for this. It is a Chinese root method that I know for a fact works, where Kingoroot and Towelroot fail. Trust me, I tried Kingo and Towelroot just as many times as you. It also installs it's own sub-par version of Superuser called Kinguser. Nothing great, but it gets the job done. If you only want root, you are done. Install the app, run the app, run Root Checker. From here you can uninstall system apps, overclock, etc. Keep in mind, if you uninstall either of these, you lose root access.
If you want a custom recovery/ROM, here's how:
First thing I did was flash the recovery. But it has locked bootloader right? Right. So we are going to Odin flash the recovery. Although it is a custom recovery, flashing through Odin will allow you to bypass the bootloader lock. First, you will want to download the recovery image. http://www.mediafire.com/download/j6...teaio_twrp.img
Now put this somewhere you can find it.
Next you will need to download the .tar converter tool and convert this .img file you just downloaded into a .tar.md5 file so that Odin can flash it. There are instructions in the link and it is very simple.
Once you have converted the img, Open Odin, and boot your phone into download mode by holding Volume down and power, and plug it in. Odin should notify you it has been "Added!" Select PDA, and navigate to the recovery img that you just converted to the tar file. Select this file, then make sure Auto Reboot is the only other box checked, and hit start. It should only take a few seconds, and you should be greeted with a "Success" message. Allow the phone to reboot into recovery. It should do it manually, but if not, boot into recovery by holding Volume Up+Home+Power. It should load the TWRP splash screen. If this happens, it was all successful.
That is the hard part honestly. Once you're recovery is installed, you're golden, Pony Boy. Download a compatible ROM and install the zip via TWRP recovery. Unfortunately, from what I understand, Touchwiz based ROMs are the only ones compatible with this method. I am using Skyfall as suggested in another thread I saw, and it is great. Looks just like stock, but enables Wifi Tethering (which Cricket currently blocks) and comes with a couple other cool features. It also uses Aroma installer which allows you to customize the installation, meaning you can choose to have Xposed Modules and Wanam Xposed installed by default, and NONE of the Samsung apps from default.
Here is the link for a ROM that I know for a fact works flawlessly: http://forum.xda-developers.com/show...01&postcount=4
KEEP IN MIND---Cricket/Aio must install the AT&T variant from Aroma installer. Others may work, but this is the only one I can confirm. Internally, they are the same phone. LTE, Wifi, Bluetooth all confirmed working.