This guide supports the ASUS TF300T (wifi) model only
This guide supports the following ASUS Android 4.2 firmware numbers:
V10.6.1.15.3, V10.6.1.27.1, and 10.6.1.27.5.
This guide does not support the Android 4.2 10.6.1.8 firmware or lower. You can find out what firmware you have by going into Settings-> About Tablet and reading the “Build Number” If you do not have the right firmware, you will need to upgrade via OTA or manually.
Last Updated March 2015 (Just a little bit)
I will preface this guide with a sincere thank you to Transformerforums user “Droidbound.” This a slightly modified version of his original guide here for the tf700 re-posted for the tf300. I was also inspired by Frederuco’s guides for the Tf101 here and wished that one had been available for me when I started rooting my tf300. Believe me I was extremely scared about everything at first
I want this to be a complete and up to date guide covering ROMing on the tf300, many of the guides found on the internet and xda are outdated or unmaintained. Some of them don’t even reference the latest ASUS bootloaders and the instructions in them can cause bootloops, bricking, or other problems.
I thought it would be especially helpful to add information relating to both jelly bean ROMs as well as the newer KitKat ROMs which have now become available from Cyanogenmod and Omnirom.
I hope this guide will make it a little easier for those users who wish to unleash the potential of this tablet but have no idea where to start. This is meant to be for inexperienced users who may be flashing for the first time.
If you find information I provide here to be incorrect or outdated, please do chime in!
And the standard disclaimer: I am not responsible if you misunderstand instructions I give here, if my instructions are wrong, if you forget to charge the battery and the tablet dies halfway through a flash or if your house goes up in flames.
YOU DO THIS AT YOUR OWN RISK
Part 1: Unlocking and Installing a Custom Recovery
First things first:
Backup everything on your tablet you care about to an external microSD or your PC. Don't worry about your apps. You can always install them from the Play Store.
This is just common sense. It is not inherently risky to flash custom ROMs. If you are following these guides and do not simply “flash without reading” there is little chance you can screw things up
Basically the process of flashing a custom ROM on the T300 involves three steps:
1) Unlock the bootloader using Asus' Unlock tool. (This allows us to gain the ability to install custom recoveries in the next step)
2) Install a custom recovery on the tablet (this is almost like a “mini operating system” which lets you modify the rest of the tablet in an isolated system. This includes making and restoring backups as well as installing ROMS)
3) Flash a custom ROM of your choice using said custom recovery. (I will include some links to notable ROMS as well as a description of each and installation instructions in the second post of this guide.
1. Unlocking the bootloader (See all the updates below these instructions: things have gotten a bit more complicated
)
Please make sure that your tablet has a fairly full charge on it (or is connected to a charger) whenever you are doing these steps. It would be a terrible tragedy to follow all the steps correctly only to “brick” the tablet when the battery dies in the middle of installing something.
• Make sure "USB debugging" is checked in Settings > Developer Options (if you don't see it, go to About Tablet and tap 7 times on Build Number)
• Go to Asus website: ASUSTeK Computer Inc. -Support-
• Select your device (ASUS Transformer Pad TF300T), choose "Android" for OS and look for the "Utilities" on the resulting page.
• Download the “Unlock Device App: Unlock boot loader.(Only works with TF300T 4.2 JB OS)”
• The tool downloads as a .rar file which is an archive you have to decompress. 7zip is a free and very good Windows tool that will do it for you
• On your tablet, in Settings > Security check "Unknown Sources"
• Copy the .apk you extracted from the .rar archive to your tablet.
• Find the apk in your tablet's file browser, tap it and let it install
• Open the app and follow the instructions. You will loose your warranty as soon as you click "I agree".
*Update* It seems that users sometimes have problems with the unlock app due to Google labeling it as "less secure" There is a Google Account setting to change that should fix things right here. https://www.google.com/settings/security/lesssecureapps
*Update* July 2015: And another wrinkle... It seems to be pretty consistent now that the Unlock Tool hangs on the Google account password step. I suspect something changed on the Google side. It probably doesn't allow the tool to check/compare the password anymore. There have been quite a few security changes lately and the unlock tool never gets updated so I suspect that Google now is blocking access by the tool to it's servers.
The work-around is easy enough: Delete the Google account from the tablet (Settings > Accounts), then run the tool again. If that doesn't do it, do a factory reset from Settings, reboot and during the initial setup establish a WiFi connection but skip the google account setup, then run the tool
*Update* December 2015:
So it looks like Asus decided to remove all the old Transformer support drivers and firmware off their site for some regions. That includes the unlock tool. Luckily for us, We have a copy of the tf700 v7 app saved from destruction by Kevinthefixer (let's all give Kevin a round of applause!) \
UnLock_Device_App_V7
I can't test this but I am told it works the same way as always. If you run into trouble try the trick posted above that mentions removing your Google account. Otherwise post in this thread and someone will be able to help you out.
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To check if you are unlocked, boot the tablet and read the tiny script. It should say:
The device is unlocked.
This can be a 5 Minute operation that goes without a hitch or a very frustrating experience with lots of error messages. There is no definite rhyme or reason for this. For some people it works like a charm, for others it works after 15, 25 or 35 attempts, for some never.... This problem is widely discussed on several forums. For now I assume it goes ok.
To check if you are unlocked, boot the tablet and read the tiny script. It should say: This device is unlocked.
2. Installing a custom recovery on your tablet
I highly recommend you choose TWRP as your custom recovery.
This is the trickiest part of the whole process. To push TWRP to your tablet you need to set up "Fastboot" between your tablet and your PC. Fastboot is a protocol that enables you low level access to your tablet.
Practice/Background
Power down your tablet and disconnect it from the dock
Push and hold the Volume Down key (left side of the rocker) and the Power key at the same time. Let go when you see the tiny script. Read it and it tells you that your tablet is now in fastboot mode
You are now in the JB bootloader menu where you see 3 icons: RCK, Android, Wipe Data
IMPORTANT! You should have three icons in your bootloader. If you have 4 do not proceed from here. You need to upgrade to the newest 4.2 bootloader
RCK - (which should be flashing) is your recovery (the stock recovery at this point, but once TWRP is installed this is one way to get into it)
Android - is your system, selecting it boots you back to into your ROM. This is what is known as a cold boot.
Wipe Data - stay away! Especially with custom software installed never, never use this option!
To toggle between the three icons use Volume Down, to select one use Volume Up. Try it but do not push Volume Up when the 'Wipe data' icon is flashing!
In case you ever get into a bootloop from doing this, we now have a very helpful guide HERE for getting out f it.
Now you need to install the fastboot on your PC (I will only deal with Windows instructions as I cannot vouch for any OSX or Linux guides. You can Google methods to install fastboot drivers as there are many different ways to accomplish the same thing)
For Windows users I recommend the 15 Second ADB tool [TOOL] [WINDOWS] ADB, Fastboot and Drivers -… | Android Development and Hacking | XDA Forums (easy instructions on XDA thread page)
If you have OS X I cant provided any assistance but here is a reputable guide [GUIDE] Set up ADB and Fastboot on a Mac eas… | Android Development and Hacking | XDA Forums
If you have Linux, I think most distributions have the packages for ADB and Fastboot installed out of the box.
- Run the Installer executable file and answer yes to all the prompts.
- IMPORTANT: Dont forget to agree to installing device drivers or you likely wont have success with any of your commands.
- Boot the tablet into fastboot mode and connect it to your computer via the original USB cable
- In Windows Explorer navigate to the folder that contains your adb.exe and fastboot.exe. For the 15 second tool this is a folder in your C drive directory
- Press Shift + right click and select "Open command window here".
- In the command window on your PC type:
- If that command returns a string of numbers and letters, you are good as gold.
- If it returns: "No devices found", fastboot is not working - yet - and you have to troubleshoot.
Getting the correct drivers working can be the hardest part of this exercise. If your computer does not "see" the tablet in fastboot, you may have to google another method that will work better for your system. In Win8 you seem to have to disable a "Windows Driver Verification" setting in system settings. I have embedded a video below which goes over that procedure as well as using another tool called Minimal Fastboot and ADB (Credits to XDA and also Droidbound for originally linking it)
Let's assume everything is good:
•On your computer go here. [RECOVERY] KANG TWRP TF300T 2.8.x.x@AREA51 J… | Asus Transformer TF300T | XDA Forums
This is a special recovery made for only tf300s on the 4.2 bootloaders mentioned at the top of this post. This is not the "official version, rather a "kanged" version with bugs ironed out. It is known to be much more stable than the official versions.
Download the latest build available from the link in the second post on XDA. It should come through as a .img file
• Rename the file to twrp.img (or whatever you like but remember what it is called) and place it into the same directory as your fastboot.exe in the ADB Fastboot Tool folder. For example, my directory was C:\Program Files (x86)\Minimal ADB and Fastboot. Make sure your computer is showing extensions properly so that you don't accidentally have twrp.img.img 
• Again check the connection to the tablet with:
If you get the connection, in the command window type:
Code:
fastboot -i 0x0B05 flash recovery whateveryounamedit.img
This will flash the recovery to the recovery partition
If it is successful you will see something like this:
C:\Program Files (x86)\Minimal ADB and Fastboot>fastboot -i 0x0b05 flash recovery twrp.img sending 'recovery' (6448 KB)...
OKAY [ 1.856s]
writing 'recovery'...
OKAY [ 6.624s]
finished. total time: 8.487s
If you see the word finish then the recovery has been flashed, but you need to reboot into android for it to take affect.
Use the command:
and let the tablet boot up normally.
Or if that doesn't work you can hold the power button.
Open Recovery and Create a Nandroid
Your almost there! You are now on the stock ROM with a custom recovery installed.
Power the tablet down and boot into the bootloader menu with Volume Down and Power buttons.
With RCK flashing, push Volume Up and you should boot into TWRP. Familiarize yourself with the many options of the touch based interface without executing anything yet. TWRP is very user friendly. You basically cannot do anything of consequence "by accident", so don't be shy.
twrp 2.5.jpg
Touch "Backup", leave the default selection as they are and swipe the button to create a nandroid (a backup) of your current system.
This is a very healthy habit to develop: You always want to have a nandroid of your last working system squared away so that you can do a simple restore if you flash something that does not work, or something goes wrong during a flash. With a working recovery and a good nandroid you are minutes away from a working system if you soft brick your tablet. These backups are located in your Sdcard/TWRP directory if you ever need to remove them from the tablet or delete them. These backups are typically between 3-6GB and only include your operating system, preferences, and all applications. They do not include your files, songs, pictures, movies, etc. If you want to restore a Nandroid you can easily do so by touching the restore button in TWRP. This will "wipe" any previous data and replace it with the data included in your backup. Note: any files, pictures, etc. which are not backked up will not be touched when restoring nandroid.
You can out of recovery by selecting Reboot and System on the following screen.
OK, so this concludes the first part of my guide on ROMing TF300s. I will continue this guide below with additional sections on using TWRP and installing ROMS.
In the meantime, feel free to post below and ask questions.