This method is now obsolete and not needed, we are able to root directly onto 4.3 now thanks to geohot, please see towelroot thread: http://forum.xda-developers.com/show....php?t=2783157
Unfortunately there is no method to root directly on the Xperia T/TL/TX/V with Android 4.3, we must downgrade first!
Step 1, Getting flashtool installed:
You need to download flashtool and install the latest drivers, this can all be found here and here
Step 2, Getting your device running Android 4.1.2 which is rootable!:
You need to download a 4.1.2 FTF file, I recommend using this one if you are an Xperia T user,
Use this one if you are an Xperia V user.
Use this one if you are an Xperia TX user
although any will do as long as has a build number earlier than 9.1.A.1.141
Next what you need to do is open up flashtool which you installed in Step 1. Next click on the lightning bolt button which is the flash button, flashmode should be selected by default, click OK!
Now you are in the firmware selection area, navigate to where you downloaded the FTF file using the browse button in the top right.
Select the correct firmware, then click OK!
It'll process a bit, then will tell you to connect your device, firstly put your cable into the computer/laptop first, then hold down the volume down button on your device and connect the micro USB part to the device.
If all goes well it will start flashing, finish and tell you to restart the phone, the process could easily take 15 minutes, so be patient.
Step 3, Lets root the device:
Try rooting with the root option within FlashTool
Should that not work try this:
You want to download bin4rys rooting toolkit, which is found here and here
This part you will be walked through in the command prompt of the toolkit, it will tell you what to do and when, it is very simple!
Step 4, Now we're rooted, we want a recovery:
Now we need to get CWM recovery for locked bootloaders installed!
Download CWM installer here
Next extract the folder to somewhere on your computer, connect your phone to the computer, remember to allow unknown sources to be installed and to allow usb debugging, these can be found in 'security' and 'developer options' respectively.
Once done, double click on 'install.bat' and let the installer do it's magic.
If you have issues with this step, take a look at the 'Unable to enter recovery' section in the CWM for locked bootloaders thread here
Step 5, Download a rooted 4.3 update:
If you are an Xperia T user download from here
If you are an Xperia V user download from here
If you are an Xperia TX user download from here
Now transfer the package to the SD card on your device.
Next you want to power off your device, once that is done power back on, when you hit the first vibrate you should see a blue led, start repeatedly pressing the volume up button, the led should turn green and you will enter into CWM recovery.
RECOMMENDED: Now you are in recovery you should do a complete wipe data/factory reset, now this can be skipped but if it leads to errors and problems then you may need to go back to step 1, you have been warned!
Head to install zip from SD card and locate to where you downloaded the file, then flash the file!
Step 6, Enjoy:
You should now be all up to date with Android 4.3 and have root access, feel free to comment and ask questions in the thread if you are having problems or things didn't work as they should.
You also now should have PhilZ Touch Recovery installed which will allow you to install mods, make backups etc. To enter it is the exact same procedure as for CWM earlier on!
I hope this has been a pain and stress free experience for you and that it worked