[Thinkpad Tablet General] drwakey:
Hello there!

After searching the internet up and down for a guide how to root this device and having found nothing, i decided to do it by myself - with success.

Here i want to share my way of unlocking this device for others:

Warning: Backup all your data first, as the unlocking of the device will reset it to factory defaults!

This is a guide for people who are aware of the risks of flashing, it lies completely in your own responsibility!

Before doing anything at all, read this post carefuly!

Requirements:

Lenovo Yoga Tab 3 8 / YT3-850F (obviously)

Having ADB and fastboot installed.

Getting a proper twrp version & Chainfires SuperSU

Links:

15 seconds ADB Installer v1.4.3: https://xdaforums.com/showthread.php?t=2588979

Fitting twrp: http://www.htcmania.com/showthread.php?t=1291696

The thread's in spanish, i used google translate.

Chainfires SuperSU: https://download.chainfire.eu/1014/SuperSU/SR5-SuperSU-v2.78-SR5-20161130091551.zip

This one worked for me, first i flashed an older version and got stuck within a bootloop. Reflashing this newer version and wiping all caches within twrp helped.

Step by step:

1. First you want to unlock the "developer options" in your settings.

To do this go into settings -> about this device and tap on "BuildNumber" 7 times.

After two taps, a small pop up notification should appear saying "you are now X steps away from being a developer" with a number that counts down with every additional tap.

unlocked developer options.

2. Now you can go into the developer options and activate both "USB debugging" and "OEM Unlock".

Both are needed for beeing able to flash anything onto your device in the first place.

3. Install Lenovos USB drivers & the 15 seconds ADB Installer v1.4.3

4. Boot your device into Recovery Mode. To do this, turn it on while holding both the On-Button as well as Volume-Up.

Inside the Recovery console select "boot into bootloader" with the volume keys and confirm with the on button.

See: https://xdaforums.com/wiki/Lenovo_Yoga_Tab_3_-_8"-_YT3-850F

5. Connect your Tablet to your PC via USB.

Now open a console prompt on your PC and Type "fastboot oem unlock" (without the quotes of course).

This should unlock the bootloader for flashing.

6. Flash the twrp image supplied in the links section.

For Android 6 extract the "TWRP 3.0.2.7 (a)" folder from the downloaded archive, for Android 5 the "TWRP 2.8.7.7" folder.

Inside this folder, there should be a folder called "img", enter it.

Inside the img folder open a new console by “Shift + Right click” on any empty white space inside the folder and then select “Open command window here” from the context menu.

Now type "fastboot twrp.img", this should install twrp onto your device.

Now type "fastboot reboot" to reboot your device.

See: http://rootmygalaxy.net/install-twrp-recovery-via-fastboot/

Note: I have done this step on Android 6, so noe guarantee for Android 5.

7. You can enter twrp the same way now like the original recovery menu.

It will boot up in russian language, but you can change it to english or some other choices:

[IMG="How to change twrp language"]http://xiaomitips.com/media/2016/06/Change-TWRP-Language-CN-to-EN.jpg[/IMG]

8. It is advisable that you do a backup of your system files now with twrp, in case something goes wrong with SuperSU.

9. Copy the zip of Chainfires SuperSU onto your Device.

Within twrp you can now install SuperSU, which will root your device.

10. Done! Enjoy your newly rootet device!

Final words: To the moderators: Feel free to edit this thread for better understandability.