After hours of researching and looking a threads, I managed to get KitKat 4.4.2 on my phone followed by Kitkat 4.4.4 and ROOTED!
Here is my guide to save you all time. I will not be responsible if you brick your phone. If you brick your phone use Sony's PC companion to repair your phone.
This Guide was tested and worked on my XPERIA Z C6606 Tmobile Locked Bootloader. On Windows 7 PC.
Have [[NOT]] tested on other XPERIA devices and would not recommend it on other devices.
[[BACK UP ALL DATA to your PC]] All data on your phone and SD card will be wiped!
1. root current xperia z android phone using geohut's towelroot tr.apk
b. goto file, save page as "tr.apk"
c. connect the phone access sd card and create a new folder called "apps".
d. Put tr.apk in the apps folder you just newly created on your sd card.
e. then use a file explorer to navigate to the apps folder on your sdcard and install tr.apk.
f. download rootchecker off the play store to check if rooted.
2. install latest flashtool
3. dowwnload kitkat 4.4.2 (C6616_10.5.A.0.230_Customized_US.ftf)
b. go to my computer, c:/ and select the flashtool folder and open the firmwares folder
c. place C6616_10.5.A.0.230_Customized_US.ftf in the firmwares folder
d. open flashtool
e. connect phone to flashtool
f. click on flash icon
g. for bootmode chooser select "flashmode"
h. select firmware: [device] C6616 [version] 10.5.A.0.230 [BRANDING] Customized_US
i. click on flash and follow the prompts.
j. will require you to turn off phone
k. hold the volume down button as you reconnect USB and flashing starts.
l. when completed flashtool will prompt you to remove phone.
remove phone power on and let it load for the first time it will take a couple minutes.
4. You are now on Kitkat 4.4.2!
A. go to settings
B. Select about phone
C. go down to build number
D. it should say "10.5.A.0.230" Click on it 8 times to enable developer mode.
E. go back to home screen on settings and "developer options" should appear.
F. click on developer options and check enable USB Debugging.
G. also go to home screen on settings and select "security" and check "unknown sources"
then re-root phone using tr.apk
H. You should get a Software Update from Sony telling you Kitkat 4.4.4 build 10.5.A.0.238 is available. OR go to "Settings", about phone, and click on "software update"
4. To root Kitkat 4.4.4 go to this thread below.
I used GeoHut's tr.apk to re-root my phone.
Stamina Mode "On" has random restarts.
Connectivity with Mobile Data is not 100% everywhere you are at... (maybe because the baseband is taken off a c6616) [[[FIXED]]] see below:
Go to Settings:
-Under Wireless & Networking select "More..."
-Go to Mobile Network Settings
-Select Access Point Names
- ADD a new APN or edit existing. Use settings below.
I would recommend downloading SuperSu from the Playstore and granting permissions to it.
Credits go to:
Androxyde for Flashtool
Chainfire for SuperSU
Geohot for the original towelroot exploit
NUT for kitkat 4.4.2 US customized .ftf flash file.
KingVortex for writing up the guide to root kitkat4.4.4
Lastly, I should get some credit for compiling this guide.