[Transformer TF300T General] berndblb:
I have been asked to port my "Beginners Guide" from the TF700 forum for the TF300. Since both tablets are very similar, that was not too hard to do ;)

If I have missed to update a link specific for the TF300, do let me know please.

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

These instructions assume that you are on the latest Asus bootloader: 10.6.1.27.5

To determine which bootloader you currently have:

From an "Off" state, boot the tablet with Volume Down and Power into the bootloader menu. Read the small script in the upper left. You'll see

US_epad-10.6.1.27.5-20130801" or similar.

US or WW, JP, CN is your SKU or region

10.6.1.27.5 is your bootloader version

20130801 is the build date (and immaterial in most cases).

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. But something can wrong at any time and you have to be careful. If you are, this is a safe procedure.

Basically the process of flashing a custom ROM on the TF300 involves three steps:

1) Unlock the bootloader using Asus' Unlock tool

2) Install a custom recovery on the tablet

3) Flash a custom ROM of your choice using said custom recovery​

Unlocking the bootloader

Your tablet should be fully charged at this point!

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: https://www.asus.com/support/Download/28/1/0/9/8BmzkQ4yoz5WzBrW/32/

Choose "Android" for OS and look for the "Utilities" on the resulting page.

Download the Asus Unlock Tool v7 (not v8! It says v7 is for ICS but it'll work fine on JB - see below)

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".

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 55 attempts, for some never.... This problem is widely discussed on several forums. Google it if you hit that roadblock.

To check if you are unlocked, boot the tablet and read the tiny script. It should say:

The device is unlocked.

Installing a custom recovery on your tablet

I highly recommend you choose TWRP as your custom recovery. If you want CWM, you are on your own.

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 until you feel the tablet vibrate twice. Let go when you see the tiny script. Read it and it tells you that your tablet is now in fastboot mode and you will see three icons (I assume again you are on a JB 4.2 bootloader. In older bootloaders you had 4 icons and had to select the USB icon to get into fastboot mode):

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.

Wipe Data - stay away! Especially with custom software installed never, ever 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!​

Installing ADB and fastboot plus the necessary drivers

For a working ADB/fastboot connection from PC to tablet you need:

a) Asus device drivers – if you connect the tablet to your PC and it's recognized as a portable device you should be ok. If not, download the Asus Sync Utility from their support/downloads site and install it to get the drivers, then uninstall the program from your PC if you don't want it. The drivers will stay.

b) Fastboot and ADB drivers which will be installed if you run the tool below.

Windows Vista, 7, 8, 10:

Download and run this cool little tool [TOOL] [WINDOWS] ADB, Fastboot and Drivers - 15 seconds ADB Installer v1.1 - xda-developers (don't forget to hit the Thanks button)

The tool installs the adb and fastboot.exe to a folder on your C:\ drive (look for adb) and the corresponding drivers. Takes about 15 seconds.

On Windows 8 and 10 you need to turn off the driver verification feature. Here's a great video on how to do it:

https://www.youtube.com/watch?v=afrvSGiMAtk

Or - even better - here's a quick command line toggle to achieve the same (thank you [MENTION=7965400]Jack_Hardin[/MENTION]):